Institute of Pathology Medical Faculty University of P. J. Šafárik Andrej Böőr, Ivan Jurkovič, Marián Benický and Zuzana Havierová Practical lessons in histopathology and methods in pathology Košice, 2004 1 CONTENTS Introduction ……………………………………………………………………………….......……7 A. Methods in pathology 1. Autopsy…………………………………………………………………..………………...................8 2. Surgical pathology…………………………………………………………………....11 3. Cytopathology………………………………………...…………………………....…15 4. Immunohistochemistry………………………………...……………………………...17 5. Electron microscopy……………………………………..………………………..….20 6. Enzyme histochemistry……………………………………...…………………….….22 7. Diagnostic molecular pathology……………………………………………..…….…23 8. Cytogenetics…………………………………………………………...………….…..25 9. Informatics……………………………………………………..……………………..26 10. Quantitative methods (histometry)……………………………………………...…….29 11. Microscopic technique………………………………………………………………..29 B. Practical lessons in histopathology 1. Cell necrosis of renal tubules………………….……………...……………………..31 2. Caseous necrosis of the lymph node…………………………...………………........31 3. Liquefaction necrosis of the brain...............................................................................32 4. Atrophy of the liver (brown atrophy)..........................................................................33 5. Fatty infiltration of the heart.......................................................................................34 6. Extracellular hyaline changes (hyaline arteriolosclerosis of the kidney)....................34 7. Hyaline droplets in the renal tubules...........................................................................35 8. Hyaline changes in splenic capsule.............................................................................35 9. Fibrinoid necrosis (degeneration) in rheumatoid nodule.............................................36 10. Amyloidosis of the kidney...........................................................................................36 11. Fatty change of the liver (fatty liver)...........................................................................37 12. Virus-induced cell injury (molluscum contagiosum)..................................................38 13. Dystrophic calcifications in the heart..........................................................................39 14. Cholesterol crystals in the epidermal cyst...................................................................39 15. Exogenous pigmentation (anthracosis of the lung)......................................................40 16. Hemosiderosis of the liver...........................................................................................41 17. Silicosis of the lung......................................................................................................41 18. Hypertrophy of the heart..............................................................................................42 19. Chronic passive congestion of the liver (”nutmeg liver”)...........................................42 20. Chronic passive congestion of the lung (brown induration of lung)...........................43 21. Thrombosis (mural thrombosis in aorta).....................................................................44 22. White infarct of the kidney..........................................................................................44 23. Red infarct of the lung.................................................................................................45 24. Pulmonary edema........................................................................................................46 25. Acute serous inflammation of small intestine..............................................................46 26. Chronic inflammation of the nasal cavities.................................................................47 27. Acute purulent (suppurative) meningitis.....................................................................48 28. Acute purulent appendicitis.........................................................................................48 29. Chronic granulomatous inflammation (tuberculosis of the lung)................................49 30. Chronic granulomatous inflammation (sarcoidosis of lymph node)...........................50 31. Granulation tissue (inflammation in the (sub)chronic stages, connective tissue repair)...........................................................................................................................51 32. Organized and recanalized thrombus...........................................................................52 33. Chronic granulomatous inflammation around foreign bodies (foreign body granuloma)…………………………………………………………………………...52 34. Squamous metaplasia of cylindrical epithelium..........................................................53 35. Pseudotumor (epidermoid cyst)...................................................................................54 36. Preneoplastic disorder (cervical dysplasia)..................................................................54 37. Carcinoma in situ (intraductal carcinoma of the breast)..............................................56 38. Metastasis of carcinoma in the lymph node.............................…................................56 39. Characteristics of malignant neoplasms (parenchyma and stroma, anaplasia, and atypical mitoses)..........................................................................................................57 40. Fibroma........................................................................................................................58 41. Fibrosarcoma...............................................................................................................59 42. Lipoma.........................................................................................................................59 43. Chondroma...................................................................................................................60 44. Osteoma.......................................................................................................................60 45. Chondrosarcoma..........................................................................................................60 46. Cavernous hemangioma...............................................................................................61 3 47. Leiomyoma..................................................................................................................61 48. Malignant fibrous histiocytoma...................................................................................62 49. Squamous cell papilloma of the oral cavity.................................................................63 50. Papillary carcinoma of the thyroid gland.....................................................................63 51. Squamous cell carcinoma of the lip.............................................................................64 52. Basal cell carcinoma of the skin (basalioma)..............................................................65 53. Transitional (urothelial) cell carcinoma of the bladder...............................................65 54. Adenocarcinoma of the colon......................................................................................66 55. Neurinoma...................................................................................................................67 56. Pigmented nevus of the skin (nevocellular nevus)......................................................67 57. Malignant melanoma of the skin.................................................................................68 58. Benign teratoma (adult cystic type) of the ovary.........................................................68 59. Fibroadenoma of the breast..........................................................................................69 60. Seminoma of the testis.................................................................................................70 61. Choriocarcinoma..........................................................................................................70 62. Infective (bacterial) endocarditis.................................................................................71 63. Acute myocardial infarction........................................................................................72 64. Healing myocardial infarction.....................................................................................72 65. Myocarditis..................................................................................................................73 66. Atherosclerosis of the aorta.........................................................................................73 67. Polyarteritis nodosa......................................................................................................74 68. Acute purulent bronchitis.............................................................................................75 69. Bronchial asthma.........................................................................................................75 70. Bronchopneumonia......................................................................................................75 71. Lobar pneumonia.........................................................................................................76 72. Primary atypical pneumonia........................................................................................77 73. Fibroplastic pleuritis (pleurisy)....................................................................................78 74. Squamous cell carcinoma of the lung..........................................................................79 75. Small cell carcinoma of the lung.................................................................................80 76. Extramedullary hematopoiesis.....................................................................................80 77. Chronic lymphocytic leukaemia (CLL) in the liver.....................................................81 78. Chronic myeloid leukaemia (CML) in the liver..........................................................82 79. Non-hodgkin´s lymphoma in lymph node...................................................................83 80. Multiple myeloma (plasmacytoma).............................................................................83 81. Pleomorphic adenoma of the salivary gland................................................................84 82. Esophageal varices.......................................................................................................85 83. Chronic peptic ulcer of the stomach............................................................................86 84. Chronic gastritis...........................................................................................................87 85. Transmural infarction of small bowel (infarsatio hemorrhagica intestini tenuis).......88 86. Carcinoma of the stomach..............................................................….........................89 87. Subacute hepatic necrosis............................................................................................89 88. Micronodular hepatic cirrhosis....................................................................................90 89. Hepatocellular carcinoma in cirrhosis.........................................................................90 90. Chronic cholecystitis....................................................................................................91 91. Acute hemorrhagic pancreatitis...................................................................................91 92. Polycystic kidney disease............................................................................................92 93. Benign nephrosclerosis (arterionephrosclerosis).........................................................92 94. Membranoproliferative (mesangiocapillary) glomerulonephritis................................93 95. Acute pyelonephritis....................................................................................................94 96. Nephroblastoma (Wilm´s tumor).................................................................................94 97. Renal cell carcinoma (adenocarcinoma of kidney)......................................................95 98. Hydronephrosis............................................................................................................95 99. Benign prostatic hyperplasia (”hypertrophy”).............................................................96 100. Mucinous cystadenoma of the ovary.................................................................96 101. Serous cystadenocarcinoma of the ovary..........................................................97 102. Ectropion of the cervix......................................................................................97 103. Cystic glandular hyperplasia of the endometrium.............................................98 104. Carcinoma of the uterine cervix........................................................................98 105. Carcinoma of the endometrium.........................................................................99 106. Spontaneous abortion........................................................................................99 107. Hydatidiform mole..........................................................................................100 108. Suppurative salpingitis....................................................................................101 109. Tubal pregnancy with abortion........................................................................101 110. Fibrocystic disease (fibrocystic changes) of the breast...................................102 111. Invasive lobular carcinoma of the breast.........................................................103 112. Hashimoto´s thyroiditis...................................................................................103 113. Colloid goiter of the thyroid............................................................................104 114. Pituitary adenoma............................................................................................104 5 115. Parathyroid adenoma.......................................................................................105 116. Fibrous cortical defect (nonossifying fibroma of the bone)............................106 117. Pyogenic osteomyelitis....................................................................................106 118. Osteosarcoma..................................................................................................107 119. Denervation atrophy of skeletal muscle..........................................................107 120. Nonsuppurative myositis.................................................................................108 121. Subacute sclerosing panencephalitis...............................................................108 122. Healed intracerebral hemorrhage....................................................................109 123. Oligodendroglioma..........................................................................................109 124. Meningioma.....................................................................................................110 125. Pilocytic astrocytoma......................................................................................111 126. Glioblastoma multiforme.................................................................................111 127. Benign fibrous histiocytoma of the skin..........................................................112 128. Eczematous dermatitis (Eczema)....................................................................112 129. Condyloma acuminatum..................................................................................113 130. Lupus erythematosus of the skin.....................................................................113 131. Scleroderma (Progressive systemic sclerosis).................................................114 132. Squamous cell carcinoma of the skin..............................................................115 133. Hidradenoma...................................................................................................115 134. Neurofibroma of the skin.................................................................................116 135. Chorioamnionitis.............................................................................................116 136. Amniotic fluid aspiration in the lung...............................................................117 137. Hyaline membrane disease in newborn (Respiratory distress syndrome).......117 138. Perinatal pneumonia........................................................................................118 139. Pneumocystis pneumonia................................................................................118 140. Cystic fibrosis of the pancreas (Mucoviscidosis)............................................119 Introduction The histopathologic exercises along with demonstrations in the autopsy room play an important part of the whole teaching course in general and systemic pathology. These ”practical exercises” support the theoretical lectures offering the student the possibility of a direct contact with histopathological slides for better understanding of many (albeit selected) pathological processes studied during both semesters of pathology. This manual was prepared as a study aid supporting the individual in the time of in advance study at home and namely during the practical exercises and contains basic information about all histopathologic slides, selected for our students. It is also helpful for those preparing for examination. In spite of the limited number of described lesions in this manual the students will acquire a basic knowledge and understanding of all main chapters of general pathology as well as of several human diseases and their structural features. There is an urgent need at the beginning to call attention to one of the basic conditions for making a correct histopathologic diagnosis, i.e. to reasonable knowledge of normal histology. Another condition is the knowledge of the principles of histopathologic techniques and other complementary methods. In our set of histopathologic slides practically all specimens with just a few exceptions (requiring special stains) were stained routinely with hematoxylin and eosin (HE). The most important general rules for specimen study in the light microscope are reviewed in the Chapter ”Microscopic Technique”. Individual themes were grouped according to the traditional course outline and their finding through the ”Contents” is easy. The chapter ”Methods in pathology” has been included into the text so that the student can find modern information about procedures used in daily practice of Institutes of Pathology. Authors Košice, March 2004 7 1. METHODS IN PATHOLOGY B. AUTOPSY The autopsy has served medicine in numerous ways and continues to play evolving roles in a time when technologies have dramatically improved and when new diseases, naturally occuring or iatrogenic, continue to arise on the medical horizon. Thus, despite broad-based appretiation of autopsies as a means of diagnosis and discovery, and of quality control, support for the autopsy has remained inappropriately low, in the face of increasing complexity in medical care. For several reasons the autopsy rates have much declined during the past decades in spite of the fact, that the autopsy remains the singular opportunity for a comprehensive and indeed final history and physical and laboratory examination. In ancient times the human disease was attributed to facts related first to animism, later to naturalism and to solidist theory and human dissections, described as early as 1000 B.C., were not systematically performed until the medieval period, when first autopsies have been documented, mostly when criminal behavior was questioned. Investigations of ”natural” disease-related deaths had lesser financial, political, and ethical priority (e.g. religious objections or aversion). During renaissance (16th-17th century) the interest of postmortem examinations has gradually raised. Publications by Benivieni (1507), Bonetus (1679), Boerhaave (1668-1738) and especially Morgagni (1682-1771) presented informations on causes of diseases, on autopsy methodology and activity of clinicopathological correlation. The premodern period includes the 18th and 19th century, when developments in anatomy, physiology, and pathology were advanced by many great physicians, namely Bichat, Laënnec, des Marets and the renowned contemporaries Carl von Rokitansky (born in Bohemia, lived 1804-1878) and Rudolf Virchow (born in Berlin, lived 1821-1902). They all made profound contributions to current thinking, approaches, and methodology in pathology and medicine. The autopsy technique, the individual approach or some variation may be entirely adequate, depending on the disease, its expression, and the intention of the autopsy. In the beginning of the twentieth century the autopsy was supposed to be the key process in medical education. Discovery of cause of death and acquisition of insight into pathogenesis were foremost on the list of objectives at the autopsy table. The concept of quality assurance through the autopsy was emerging. Hospital-based medicine saw the autopsy as an important measure of its general quality. PURPOSES OF THE AUTOPSY The autopsy has a pervasive influence on medical care, medical science, society in general, and the family of the deceased. One may group the points of influence into those pertinent to medical care (diagnostic-related groups, quality assurance, and total patient care), the body of medical science (research, education, transplantation, and prostheses), society (public health, vital statistics, forensic issues), and the family (counseling and understanding the life cycle). To convince other medical professionals on the importance and meaning of the highly sophisticated nature of the autopsy approach, a careful conduct of the autopsy by the pathologist performed with high standard is important and out of discussion. Otherwise, the reputation of an autopsy as a diagnostic tool suffers. Fundamental definitions related to terminologies implicit in death and autopsy are summarized in Fig. 1. CAUSE Remote cause: disease process that provides milieu or substrate for later accelerated pathologic ◄----- events -----► Proximate cause: disease or injury initiating an uninterrupted Immediate cause: reasonable and -------► series of events terminating in death forseeable complications of the initiating factor permitting the development of senous sequelae MECHANISM Physiologic derangement or biochemical disturbance attendant to death Proximate cause: DISEASE ◄--- MANNER ---►Proximate cause: INJURY ▼ ▼ ▼ Unintentional Intentional ▼ NATURAL ACCIDENTAL ▼ SUICIDE ▼ HOMICIDE ___________________________________________________________________________ DEATH 9 THE STANDARD TYPE OF AUTOPSY The routine autopsy represents a series of steps, which, if seriously performed, enable a complex insight into the health state of the deceased and serve as the basis for clinicalpathological correlations. In practice, each autopsy starts with careful study of the clinical report. This information is extremely important for the whole course of autopsy, starting with external inspection. After finishing this first step the body cavities are opened and the internal inspection called ”situs organorum” is done during which all possible lesions, their location and quantity are registered. After intrathoracic, abdominal and intracranial organs were carefully taken out (”exenteratio”) all organs are systematically inspected using a standardized procedure. The next step is dedicated to organ measurement (weight and dimensions), taking necropsy excisions and laboratory samples (microbiological, virological, parasitological, mycological, serological, immunological and biochemical, which are immediately sent to appropriate laboratories). In selected cases, also photographic documentation and eventually radiography is performed. All findings seen during autopsy are then described (or dictated) by the pathologist in the autopsy protocol on the same day and a series of macroscopic diagnoses is incorporated into four consecutive categories: 1. The main (principal) disease 2. Complications 3. Cause of death 4. Findings (diagnoses) unrelated to the main (principal) disease At the end of each autopsy protocol a brief epicrisis is added, in which the clinical and pathological diagnoses are carefully compared and the quality of clinical diagnoses and treatment is evaluated. The autopsy protocol is definitively released after completed necropsy histology studies and evaluation of all realized laboratory data. Cases characterized by relevant diagnostic discrepancies (or extremely important cases for postgradual training of hospital staff) may be chosen for discussions at the clinical-pathological conferences. The sooner the autopsy is performed after death the higher quality of histological slides is obtained, with lower level of disturbing autolysis artifacts. Additional autopsy rules are used and special procedures are recommended for postmortem examinations of children, fetuses and placenta. Certain special methods are described in autopsy monographies in relation to some extraordinary types of diseases or for e.g. conjoined malformations or post-surgery or other post-therapy complications. For all persons engaged in the post-mortem room and medical visitors during autopsies it is extremely important to comply with strict safety measures. WHY AUTOPSY RATES HAVE DECLINED Over the years, a sharp downturn in the number of autopsies has been evident and it continues to decline. Reasons most often cited are: attitudes (clinicians, families, administrators), time constraints and competing responsibilities of pathologists, physician´s fears of legal liability and of being wrong, costs, modern medical technology building false confidence, lack of inclusion of autopsy finding in death certificate and inability to request permission from families. The major consequence of medicine without sufficient autopsies is that both patient care and progress in medical science will be impeded. Hindered also will be biomedical and epidemiological research. Organs, tissues, and extracts will be unavailable, and medical student education will be hampered. The public as a whole and health professionals must be reeducated, not only as to the value of the autopsy, but also as to the practical mechanisms for reinstatement of the autopsy in the core of medical practice. The clinical physicians and pathologists should engage in a continuous dialog regarding diagnostic discrepancies (their present rate varies widely from 4 to 66%) with a view to improving the education and for betterment of future care. The most studies use a definition of discrepancy wherein the observation made at autopsy and not made clinically would have altered significantly the therapy and possible longevity of the patient. 2. SURGICAL PATHOLOGY Pathology is a medical specialty, which provides the scientific foundation for medical practice. The pathologist plays an essential role in patient care as diagnostician, patient advocate, and clinical teacher. The surgical pathologist examines all tissues and foreign objects removed from patients to identify disease processes, document surgical procedures, and release tissue for research. Surgical pathology arises from the autopsy at the beginning of the 20th century. Original designation for surgical pathology was the biopsy (from Greek words bios, meaning life, and opsis, meaning appearance). Specimens submitted for examination include all tissues with exception of materials removed for cosmetic reasons, all products od conception, all medical devices that were implanted and all foreign objects removed from body, including objects introduced by trauma. 11 It is the responsibility of all hospital personel involved to ensure that each patient´s specimen is appropriately and safely handled and processed for the maximum benefit of the patient and physician involved. When a pathologic examination is requested, the following must be provided: 1. Identification of the patient, 2. Identification of the individual requesting the examination, 3. Date of procedure, 4. Adequate clinical history with prior diagnoses, 5. Specimen identification, 6. Special handling required, 7. Timely and appropriate transport to laboratory and 8. Instructions for the disposition of gross specimens. There are five basic techniques for obtaining tissues in surgical pathology: 1. needle biopsy, 2. incisional biopsy, 3. excisional biopsy, 4. curretage, and 5. specimens removed during endoscopic procedures. Needle biopsy requires the use of a large bore needle and tissue obtained is fixed in formalin (formaldehyde) in toto (means ”on the whole”) and processed as any other biopsy specimen. On the contrary, fine needle cytology is performed by aspiration of tissue compartments and smearing on a glass slide and examined in the same fashion as an exfoliative cytology. Incisional biopsy, whether performed with a knife or a punch, is the most common method for making the diagnosis of cancer. By this method is obtained only a part of pathological lesion. If a given lesion shows a heterogenous gross appearance, it is advisable to take two or more biopsies from different areas, because sometimes a single biopsy will not show the diagnostic pathologic changes. The piece of tissue obtained should be handled with great care, because pinching of small biopsy with forceps can damage otherwise perfect material. A ”hot knife” should never be used because the margins of the lesion may be charred or distorted so that microscopic diagnosis may be impossible. Excisional biopsy is performed mainly for lesions of smaller size and because pathological lesion is removed in whole, this form is preferable to incisional biopsy, because excisional biopsy can be both of diagnostic and therapeutic value, and majority of pigmented skin lesions will be cured by this procedure. Specimens by excisional biopsy should be removed in one piece, whenever possible. Curettage is a procedure for scraping of the skin or internal surface of an organ or body cavity by special instrument (curette). More commonly it is used for scraping the mucous membrane from cervical canal and uterine cavity. All specimens obtained by various techniques should be first identified for all components. The label of the container must include the patient name, date of birth and designation of material. The gross evaluation and processing of specimens is the cornerstone upon which all other pathologic diagnoses rest. During gross examination in each specimen must be identified all anatomic structures, orientation markers, dimensions, and for some specimens also weights should be taken prior to dissection. All specimens should be completely dissected and serially sectioned. Next step in specimen processing is identification of pathologic processes with brief gross differential diagnoses of common lesion. It is often important to document the pathological change. Morphologically interesting or important specimens are to be photographed prior to fixation, if it is possible. Some lesions are best demonstrated after partial dissection of the specimen. Cross-sections of tumors offer much more information about their appearance and relationship with normal structures. The section for histological examination should be taken from area that gives best demonstration of the feature seen on gross examination, i.e. not simply a random section! For example, the best section to demonstrate penetration of the bowel wall by a colon carcinoma is the one showing the deepest extent of tumor. Margins of the specimens must be taken at the sites most likely to show tumor at the margin. For routine fixation of all specimens 10% formalin is used. This is the standard fixative and has been used in many studies including special stains and immunohistochemistry. Tissue can be preserved in formalin for many months. Some non-formalin fixatives are used for special purposes (Bouin´s solution, Zenker´s acetic fixative, Helly´s solution, glutaraldehyd, alcohol). The calcium must be removed from bone and other calcified tissues for the specimens to be sectioned. This procedure is called decalcification. The histotechnologist and the histology laboratory are essential for the accurate diagnosis of pathology specimen. Histological technique consists of tissue processing (dehydration, clearing and paraffin infiltration, tissue embedding with making blocks, and making glass slides with 4-5 um sections). 13 The tissue sections after drying are stained and provided with coverslips. For some types of biopsies, special histological stains are used and may be very helpful in any tissue, especially from liver, kidney, or bone marrow. The surgical pathology reports serve five main purposes: 1. Provide diagnostic and prognostic information for individual patient, 2. Provide information to guide the treatment, 3. Provide information for clinical databases to be used in both clinical and basic research, 4. Provide quality assurance, 5. Intraoperative consultations represent very special circumstances in the pathologist´s special expertise. There are three principal reasons to establish consultations in the operating room: a. Traditionally, the major justification has been that the surgeon has reached a point in the procedure where morphologic information is necessary for immediate operative planning. Surgical pathologist may provide also rapid gross diagnosis, but most important is the microscopic diagnosis that can guide intra- and perioperative management of a patient. During this evaluation the surgical pathologist may identify an unknown pathologic process, evaluate the adequacy of surgical margins, and identify lymph node metastases. The microscopic diagnostic information are available from frozen section only when they are appropriately technically prepared. The diagnostic information available from frozen section is limited in comparison with definitive biopsy investigation because only small portion of tissue can be frozen, the occurence of crystal artifacts, lack of special studies, lack of consultation, and relatively thick sections are evaluated. The accuracy of frozen section evaluation is reported to be 94 to 97% as compared to permanent section evaluation. An acceptable rate of major discrepancies is about 3%. Errors can be classified into next categories: 1. sampling errors, 2. interpretative errors, 3. technical problems, and 4. incorrect or incomplete clinical history. b. Tissue can be optimally processed for special studies that will be used for diagnosis (e.g. cytogenetics or electron microscopy), treatment (e.g. hormone receptor status analysis), or for research. c. Specimen can confirm that pathological tissue is present for subsequent diagnosis based on permanent sections. Most operating room consultations fall into a few general categories: bone biopsies, dermatopathology, breast biopsies (reason for consultation is mainly diagnosis of invasive carcinoma), gastrointestinal specimens (mainly for colon polyps or malignancy), pancreas (to determine whether malignancy is present), gynecologic pathology (more frequent reason for consultation is evaluation of an ovarian tumor, or endometrioid carcinoma), respiratory tract (lung and mediastinal tumors, staging of carcinoma or to identify malignancy in lung masses), soft tissue tumors, thyroid nodules (to determine whether a carcinoma is present), and lymph nodes (for evaluation of metastases or determine whether sufficient tissue is present for eventual diagnosis and special studies). Personel in pathology laboratory handles potentionally infectious material every day. It is estimated that e.g. about 50% of the patients who are HIV positive are undiagnosed at the time of admission to the hospital. Therefore, it is important to limit the risk of infection by handling all specimens with the utmost precaution. 3. CYTOPATHOLOGY Even though isolated cells were visualized in the microscope over 200 years before histology was born in 1839 by Purkyně´s introduction of the microtome for sectioning of tissues, cytologic techniques were not developed until the 1920s. In the late 1920s a procedure was designed for the diagnosis of cancer from exfoliated cells simultaneously by professor George N. Papanicolaou (1883-1962) in New York, U.S.A. and professor Aurel A. Babeş (1886-1961) in Bucharest, capital of Romania. Aspirated material was used to diagnose cancer a century before the technique was popularized as a routine diagnostic procedure by drs. Ewing, Martin and Stewart in the early 1930s in New York. Exfoliative cytology is used in diagnosis of lesions of different organs and tissues, e.g. cervix uteri and endometrium (here an reclassified international formulation is presently used called ”The Bethesda System (2001)”, oral and nasal cavity, conjunctiva and cornea or ocular chamber aspirate. Exfoliated cells are studied in various body cavity fluids, namely from pleural, peritoneal or pericardial cavities and joints. Cells may also be found in gastrointestinal, bronchoalveolar, urinary and 15 peritoneal washings, in cerebrospinal fluid, in the urine and even prenatally, in the amniotic fluid (in neural tube closure defects). Frequently the sputum is examined. The use of a nylon brush and the method of brushing and obtaining mechanically desquamated cells are practised mostly in bronchi as well as in other mucosal coverings, e.g. the esophagus, stomach or large intestine. The mostly employed exfoliative cytology examination refers to cytology of the female reproductive tract, i.e. study of exocervical and endocervical smears in the frame of a mass-screening programme. Aspiration cytology using thin needle (called FNAC = Fine Needle Aspiration Cytology) is widely used in diagnosis of different skin tumors, in certain diffuse or localized organ pathologic lesions, or in a large spectrum of tissues and organs, namely in the thyroid, parathyroid and salivary glands, female and much less frequently male breast, prostate, liver, pancreas, adrenals, kidney, lymph nodes, bones and soft tissues. Localized lung lesions are aspirated either by transbronchial puctures or by transthoracic (percutaneous) aspiration cytology. Cytology may also be used for diagnosis of infections and aspirates. Touch preparations or imprints serve as an adjunct to surgical (biopsy) or autopsy histopathology. A touch specimen may also be obtained from the breast nipple and areola in non-neoplastic and neoplastic disorders. Indications for cytology according to the late professor Cardozo are: cytology for an early diagnosis, for early orientation, to help determine therapy or indicate preoperative radiotherapy, for prevention of major or even risky diagnostic procedures, its use on the operation room, to prevent hospitalization, as the only possible method, as a check of histology, for early recognition of relaps, as a check during and after therapy, for mass screening and as a tool for research. Acceptance of cytology was slow, requiring over 50 years. In the meantime, eager clinicians have substituted dubious pathologists. Exfoliative and aspiration techniques are both valuable and useful diagnostic cytology procedures. They represent an adjunct to surgical biopsy and may obviate exploratory surgery in many instances but are not to be misused and thereby discredited. This method is relatively cheap, rapid, safe and well tolerated by patients, repeatable and enables to obtain a definitive diagnosis in about 70% of cases in a very short time. Depending on the type of staining procedure the cytological slides are treated both as unfixed (”air-dried or freeze-dry method”) or fixed, mostly by concentrated alcohol or other fixatives (e.g. formalin, mercury salts etc.). As for staining of cells three most popular types of dye combinations are used all over the world: hematoxilin-eosin, Papanicolaou (”Papstain”) and May-Grűnwald-Giemsa-Romanowski stain (having several modifications). The cytoplasm accepts acid or basic stains and the nucleus, except of the nucleoli, accepts basic stain with greater intensity than the cytoplasm. For special purposes and studies also phase contrast microscopy, polarization and fluorescent microscopy, transmission and scanning electron microscopy and several other procedures including cytometry may be used. For cell concentration the use of cytocentrifuge is the preferred method of slide preparation. A part of the collected and concentrated material may be embedded in paraffin as the ”cell block” suitable for serial sectioning and application of various staining methods including immunocytochemistry. First attempts at detection of genes on cytological slides have been recently published. An access to obtaining wider range of adequate cytological samples is supported by several recently developed and available screening techniques (radiographic methods, computerized tomography, MGR, ultrasonography) and endoscopical examinations. In recent years advances in technology are used for more efficient analysis of cytology specimen, e.g. automatization, computerized high resolution scanning and quantitative measurements of cell components, tele-cytopathology consultation and real-time conferences even at long distances. There is a tendency to create a computerized automatic analyzer for cytology with artificial intelligence. Great effort is laid at the standardization and quality control. For teaching purposes many cytological monographs covering the whole field of cytology and monographs dealing with separate chapters of cytology and technology are published in several languages. Teaching slide sets prepared by expert cytopathologists are edited by the International Academy of Cytology. At least 10 national and international journals of cytology are published worldwide: ACTA CYTOLOGICA is the official journal of clinical cytology and cytopathology. National and international (european, others, and world) congresses of cytology are held all over the world each year. 4. IMMUNOHISTOCHEMISTRY Principle Immunohistochemistry is the marriage of immmunologic and histochemical methods, allowing phenotypic markers to be detected and interpreted within a morphologic context in all types of tissue. This method was introduced by Coons in 1941. Due to many technical 17 improvements of the original fluorescent-labelling method the immunohistochemistry represents an essential element of contemporary daily pathology practice. Its most widespread application is used in determination of appropriate classification of ”undifferentiated” neoplasms, the detection of their prognostic markers (oncogene products, hormone receptors, proliferation and prognostic markers) as well as for detection of infectious agents (e.g. H. pylori, Chlamydia, CMV, HPV etc.) or identification of physiologic substances in abberant locations and in inflammation (immunoglobulins, complement, fibrinogen etc.). Central to the immunohistochemical assay is the specific binding of an antibody to its corresponding antigen. An antigen is any substance that evokes an antibody response due to multiple molecular binding sites (epitopes). An antibody is an immunoglobulin (mostly of IgG class) with a specific binding domain for its corresponding antigen. During the initial period polyclonal antibodies were raised in particular animals (rabbit, swine, goat etc.) that have been challenged (immunized) with an antigen. Expressing an intense signal these antibodies also have a series of disadvantages (e.g. low avidity and specificity, cross-reacting with other antigens etc.). Monoclonal antibodies were introduced to the market later through the use of cell fusion technology (hybridoma technique). These immortalized hybrid cell lines result in the ability to indefinitively produce a unique wellcharacterized immunoglobulin (monoclonal antibody). Despite the higher cost to produce monoclonal antibodies, these purified reagents are increasingly used in immunohistochemistry. Though they have many advantages, there appear still certain limitations (e.g. undesired cross-reaction, lower sensitivity etc.). Time, temperature, and pH during the incubation of antigen and antibody will influence the binding result. Antibody dilution is a critical factor in the antigen-antibody reaction. Antibody should be always used as high a dilution as possible to obtain best staining result. Immunohistochemical assay formats Direct immunohistochemistry is the original and rapid procedure, in which the detection system (e.g. fluorochrome – FITC) is covalently linked (conjugated) directly to the primary antibody. The stained slide is then viewed in the fluorescence microscope. Indirect immunohistochemistry exploits the natural capacity of immunoglobulin to act as antigen. The primary antibody is raised in one species, for example, the rabbit, and is not conjugated. Immunoglobulins from this species are then used as an immunogen in a second species, for example, the goat, resulting in antibody recognizing immunoglobulin in the primary serum (in this example, goat anti-rabbit). Immunoglobulin from the secondary serum is then conjugated to a detection system as described earlier for the direct system. This two- layer procedure permits higher dilution of the primary antibody, enables signal amplification and increases the sensitivity. A more efficient and sensitive method called the ”three-step method” or ”antibody bridge technique” has been developed as modification of the original indirect method. In addition to the primary and secondary antibodies a tertiary-labelled antibody is used. The first and third antibody must be from the same species, and the secondary or bridge antibody is directed against that species, hence binding both primary and tertiary antibodies as a ”bridge”. The spectrum of other modern procedures includes affinity labelling methods (AvidinBiotin methods, Protein A Methods, Lectin immunohistochemistry and Immunoelectron microscopy). Detection systems, enabling visualization of the antigen-antibody complexes were first represented by fluorescein (FITC) or other suitable fluorochromes (e.g. rhodamin and several others). The study of such preparations was only possible in a relatively expensive fluorescent microscope. For more complex immunohistochemical procedures a group of enzymes is presently used, especially the horseradish peroxidase, alkaline phosphatase, glucose oxidase and β-galactosidase. Each of these enzymes is detected by a specific chromogenic substrate, e.g. diaminobenzidine (DAB), 3-amino-9-ethylcarbazole (AEC), Fast red, Fast blue, Tetrazolium blue or BCI. Such staining combinations are easily interpreted by means of a standard light microscope. A crucial requirement for a valid immunohistochemical assay is to have adequate test material that will yield valid comparative results. Methods of tissue fixation To protect the tissue from autolysis causing decrease and sometimes even loss of antigenicity the fresh, small pieces of native material must be fixed. Superior preservation of antigens is obtained by rapid freezing (liquid nitrogen). Alternatively, the fresh tissue may be fixed in water solution of formaldehyde (1:9) or in several modified formalin fixatives. In these the formaldehyde forms covalent cross-links with the antigen. This process can result in direct loss of epitopes and potentially irretrievable antigen loss. Similar antigen masking may be achieved by fixation in glutaraldehyde. Disadvantageous is also the use of coagulant fixatives, e.g. absolute alcohol, preserving better the immunoreactivity especially of filament proteins and does not creating cross-links, but causing tissue shrinkage and distortion, incomplete protection against autolysis and unwanted dislocation artifacts. Recognizing that tissue fixation is often a poorly controlled part of the 19 immunohistochemistry sequence and that tissue antigens may undergo deleterious yet reversible alteration as a result of excessive or harsh fixation, both enzymatic and nonenzymatic methods have been used in attempts to retrieve or ”unmask” target antigen. Enzymes such as trypsin, pepsin, and pronase have been used to digest tissue sections before incubation with the primary antibody. There are several nonenzymatic methods of antigen retrieval, for instance immersion of tissue sections in a strong alkaline solution or in antigen retrieval solutions, but the mostly used procedure is microwave-assisted antigen retrieval, still having some disadvantages. Immunohistochemical procedures can also be carried out on previously routinely stained slides, on decalcified or cytology specimens as well as on previously frozen tissues. 5. ELECTRON MICROSCOPY The electron microscopy has made enormous contributions, and it continues to provide new information to our understanding of the structure and function of normal and diseased tissues. Its role in routine diagnostic pathology is today quite selective, and the application of electron microscopy is now restricted to selected areas of diagnostic pathology. Immunohistochemistry has greatly diminished the use of ultrastructural studies in surgical pathology. Immunohistochemistry has several advantages over electron microscopy because it is more accessible, a special microscope is not required, immunohistochemical stains are easily compared with routine hematoxylin-eosin sections, and by immunohistochemistry may be examined many more cells than are usually studied in electron microscopic preparation. On the contrary there are some advantages of the electron microscopy over immunohistochemistry, for example in the evaluation of childhood small round cell tumors. The types of electron microscopes used in diagnostic and experimental pathology are the transmission electron microscopy (TEM), the scanning electron microscopy (SEM), and the analytical electron microscopy. Transmission electron microscopy is best known to pathologists. It relies on the passage of a beam of electrons through ultrathin section of tissue. During ”staining” the sections have been impregnated with heavy metal atoms (such as osmium and uranium), that bind to different subcellular organels and structures. The resolution of TEM can be fine as 0.2 nm, but the most diagnostic electron microscopy is conducted at a relatively low magnification, which ranges from l000x to 10000x. The scanning electron microscopy provides a threedimensional view of tissue and is largely confined to providing views of surface architecture and topographic relationship of components of tissue. Analytical electron microscopy provides information on the elemental composition of material within tissues. Immunoelectron microscopy allows the precise location of cellular and subcellular products in tissues. A marker, conjugated to antibody, serves to identify an antigen within tissue. Electron microscopy, to be properly employed as a diagnostic tool, requires attention to details so that a clinically relevant report must be provided. A representative sample of tissue must be selected, correctly fixed and processed, and then examined by a pathologist who is familiar with the corresponding light microscopy, the clinical information, and differential diagnosis issues. As fixatives employed in EM penetrate tissue slowly, only small thin pieces of tissues should be placed into fixative. Buffered glutaraldehyde is widely used to fix tissues for electron microscopy, but from practical purposes some pathologists prefer formalin and glutaraldehyd mixtures. If glutaraldehyde-fixed material was not procured, wet formalin-fixed tissue or even paraffin-embedded tissue may be used. Specimens for ultrastructural evaluation are after fixation and dehydration embedded in plastic, the blocks are sectioned by ultramicrotome at thickness of approximately l m. These so-called thick or semithin sections are usually stained with methylene blue or toluidine blue. Examination of these sections is very important, since it verifies the blocks selected are representative of the disease processes. Once the blocks for ultrastructural examination are selected, thin sections are cut by use of ultramicrotome. Results of electron microscopic investigations should not be presented as a separate report, but should be incorporated into the final surgical report. Indications for ultrastructural examinations are divided in diagnostics of non-tumor biopsies and for evaluation of the ultrastructure of tumors. Certain types of specimens require special processing for electron microscopy and here belong percutaneous renal biopsy, fineneedle aspiration biopsy, bone marrow aspirate, core biopsies of bone and body fluids. Ultrastructural diagnosis of non tumoral biopsies are more important in renal biopsies, liver biopsies, by detection of microorganisms (detection of viruses), diagnosis of storage diseases, respiratory tract biopsies, skeletal muscle biopsies, cardiac biopsies, and brain and peripheral nerve biopsies. Ultrastructural investigation plays important but selective role in the diagnostic study of tumors. The electron microscope will always provide some relevant information on a 21 problematic tumor and it sometimes is the only method whereby a firm diagnosis can be made (e.g. differential diagnosis of adenocarcinoma versus mesothelioma, differential diagnosis of poorly differentiated tumors and childhood small round-cell tumors). 6. ENZYME HISTOCHEMISTRY Histochemistry has been defined by Pearse as ”the identification, localization and quantification in cells and tissues by chemical or physical tests, of specific substances, reactive groups, and enzyme-catalyzed substances”. Enzyme histochemistry is based on conversion of the primary reaction product of an enzyme acting on a substrate to form a colored precipitate. Histochemical techniques are used selectively and are absolutely essential only for some diagnostic tools, e.g. here belongs the diagnostic evaluation of muscle biopsy specimens. Almost all currently utilized procedures in enzyme histochemistry are carried out on cryostate sections of fresh frozen tissue. Muscle biopsy must be carefully oriented to obtain cross section of fibers. Myofibrillar ATPase with acidic and basic preincubation is the most useful technique for muscle fiber typing. For examination of mitochondria succinate dehydrogenase (SDH) is the most suitable enzyme, but NADH dehydrogenase can be also utilized. Myofibrillar ATPase serves as a marker for abnormalities of the myofibrils. Acid phosphatase or alfa-naphtyl acetate esterases can be useful stain to enumerate phagocytic cells in inflammed muscle. Enzyme histochemistry is an alternative to the traditional morphologic approach to the diagnosis of intestinal malabsorption. Cryostat sections of small bowel mucosa mainly distal to the duodenum are the best material for diagnosis. The most important part of evaluation is the examination of brush-border enzymes. A semiquantitative evaluation using histochemical technique for disaccharidases (lactase, sucrose and trehalase) are usually sufficient for clinical purposes. These techniques can be utilized to identify disaccharidase defficiencies and to follow the response of patient with celiac disease to treatment. Enzyme histochemical procedures are used most extensively in diagnostic hematopathology. For example FAB classification of acute leukemias relies extensively on well-performed enzyme cytochemical reaction for classification. Presence or absence of myeloperoxidase, naphtol AS-D chloracetate esterase as a marker of neutrophilic differentiation and tartrate-resistant acid phosphatase (TRAP) in hairy cell leukemia represent the mostly used procedures. Carbohydrate moieties form important and frequently unique portion of many proteins. Many of these carbohydrates can be specifically and readily identified by their ability to bind to lectins. Lectins are carbohydrate-binding proteins of nonimmune origin and mostly of plant origin. The lectin Ulex europeus (UEA 1) is e.g. very good marker of endothelial cells, and Peanut agglutinin (PNA) has been shown to be useful marker in Langerhans cell granulomatosis. 7. DIAGNOSTIC MOLECULAR PATHOLOGY Molecular pathology is the newest subspecialty in pathology and their findings are frequently fundamental to both medical diagnoses, by solving problems in clinical practice and medical research. Molecular pathology incorporates many techniques for investigation mainly of genetic alterations in cells and microbes. There are three most important techniques: 1. Southern blotting, 2. Polymerase chain reaction (PCR), 3. Fluorescence in situ hybridization (FISH). Application of molecular pathology plays role in four main areas: 1. Identification of inherited diseases (e.g. cystic fibrosis, hemochromatosis, fragile X chromosome), 2. Identification of genes confering susceptibility to disease (e.g. BRCA 1 gene in familial mammary carcinoma), 3. Detection of organisms in infectious diseases (e.g. many viruses), 4. Identification of specific genetic alteration associated with tumors, identification of clonality in hematolymphoid proliferations and malignant neoplasms, and detection of minimal residual disease after treatment of some malignant neoplasms. Indications for use of molecular genetic pathology technique are as follows: - Clonal rearrangements of the immunoglobulin heavy and light chain genes and translocation in some types of leukemias and malignant lymphomas of B-cell origin, - T-cell proliferations with rearrangements of gamma and beta T-cell receptor genes, - Posttransplant lymphoproliferative disorders with clonal population of cells infected with Epstein-Barr virus. These studies are especially helpful for difficulty-to-classify 23 hematologic proliferations. Unlike to cytogenetics, the cells need not be viable, but Southern blot and RNA-based PCR assays are best performed on fresh or frozen tissues. Formalin-fixed and paraffin-embedded tissue is amenuable to DNA-based PCR assays. Cytologic preparations may be used for FISH techniques. - Southern blotting can be used to characterize any mixture of DNA, including highmolecular weight genomic DNA from tissue, plasmids grown in bacteria, and fragments generated in a PCR reaction. The type of DNA to be analyzed will affect the type and percentage of agarose used in the gel. Blotting technique in general are used to separate biologic molecules by size and then to transfer them to a solid support that can be probed for the molecule interest. The blotting of DNA is called Southern blotting after its inventor E.M. Southern, but RNA blots are called Northern, and protein blots are called Western, in difference to initial denomination. During this technique DNA is transfered from agarose gel to a specialized membrane, to which the DNA binds irreversibly. The membrane here named blot is then placed in a plastic bag with labelled probe in a hybridization solution. Polymerase chain reaction (PCR) is used to make large number of copies of a specific DNA sequence. Normal human genes are present at the level of two copies per cell, and viral or bacterial pathogens may be present at concentrations, which are unable to detect specific DNA sequences at such low levels. PCR allows the DNA to be copied over and over again (this process is called amplification) until it is present in sufficient quantity to be easily detected. PCR can be used to demonstrate the presence or absence of genes, to detect mutations, amplifications, or rearrangements of a gene, and to detect viral or bacterial DNA. This technique allows the amplification of a specific DNA sequence. Sample of DNA is mixed with polymerase and primers specific to the target DNA sequence. The reaction mixture is cycled through a series of temperature changes that cause repeated separation of DNA strands, binding of the primers, and synhesis of new DNA. The process allows the rapid detection of specific DNA sequences that would not be detected by other means. In situ hybridization is derived from Latin ”in situ” that means ”in its original place” and ”hybridization” that means to cause the production of a hybrid, ”across”. The basis for any hybridization assay is specificity of the interaction of a probe with target nucleic acid. This interaction shares some similarities to the antibody-antigen reaction that forms the basis for immunohistochemistry. In both instances the remarkable specificity of the interaction is caused by many weak noncovalent interactions that will be influenced by assay condition. During in situ hybridization technique tissues or cells are affixed to a glass slide, then pretreated with protein digestion, next step is interaction with the probe (known fragment of nucleic acid with label that can be detected), next step is denaturation of DNA (separation of double-stranded molecule into two single strand), than is realized hybridization (process of searching a sample for specific nucleic acid sequences), and finally is technique finished with washing, detection and interpretation of reaction. By in situ hybridization one can reveal the genotypic changes as well as oncogen expression, chromosomal mapping, infectious disease detection, and differentiate metabolic disorders. Through the hybridization process one can demonstrate not only the presence of a particular piece of genetic information, but also its specific location within the tissue, cells or chromosomes. Fluorescent in situ hybridization (FISH) is a method in which fluorescent dye-coupled nucleotides are incorporated directly into cloned DNA fragments, and after in situ hybridization to chromosome spreads, the chromosomal location of a given gene can be easily determined and compared between neoplastic and nonneoplastic cells. In addition, application of the FISH technique to interphase cells allows chromosomal amplification, deletions, and rearrangements to be detected with greatly increased sensitivity. FISH is a valuable complement to traditional cytogenetic analysis in the examination of tumors, e.g. when material for cytogenetic analysis is sparse or inadequate such as during chemotherapy or after bone marrow transplantation. FISH can be performed on fresh tumor tissue, exfoliative cells, and embedded and archival specimens. 8. CYTOGENETICS Recombinant DNA technology has found application in virtually all areas of medicine. They have application mainly for five main purposes: 1. Detection of inherited diseases (underlying the development of genetic abnormalities either prenatally or after birth), 2. Detection of acquired mutations that underlie the development of neoplasms, 3. Karyotypic analysis of pediatric and adult human tumors, considered in the past a relatively unrewarding exercise because of the seemingly random and secondary nature of the alterations, has proved to be a powerful tool for the study of these tumors, both in terms of contributing to the definition of the various entities and in providing clues to the molecular mechanisms involved in their pathogenesis (especially the germ cell tumors, bone and soft-tissue tumors, leukemias, 25 lymphomas, other hematopoetic neoplasms, epithelial solid tumors or neoplasms of unknown primary tumor site), 4. Diagnosis of infectious diseases, including HIV infection, 5. Determinations of relationship and identity in transplantation, paternity testing, and forensic medicine. Because of the labor-intensive, time-consuming nature of the conventional karyotypic analysis, new techniques have been sought for detecting numerical and structural chromosomal abnormalities in a faster and more efficient fashion. Among these the interphase cytogenetics and more recently developed comparative genomic hybridization (CGH) are used for rapid detecting and mapping DNA amplification or losses. CGH can be applied not only to fresh-frozen specimens, but also to the cell lines, and DNA extracted from formaldehyd-fixed paraffin-embedded material. 9. INFORMATICS Informatics describes the combination of basic and applied sciences to the processing of data and information. When applied to medically related information, the term ”medical or healthcare informatics” is used, encompassing the expanse of healthcare computing interests. Its scope includes clinical science, computer science, decision science, aspects of engineering, library science, and information science. The practice of pathology produces vast amounts of data, which are communicated to physicians and others. As these individuals process the data, it becomes information that guides clinical decisions. The data and their availability influence greatly the decisions made in the care of the patient. The pathologist in the role as an information officer or manager with interest in and knowledge of the computer hardware and software systems can provide that function. A basic condition for this is achievement of computer proficiency (computer literacy) during the training period. The so-called decision support representing a new discipline is focused on two areas – test performance and medical utility. Recent applications of these tests have been performed especially in cost-effectiveness analysis. In the future, informatics will be recognized as a distinct discipline in medical practice. The pathologist is in a unique position to capitalize on the current opportunities because of the long experience of laboratory computerization. Features of laboratory information system (LIS) Advantages Access to information: in most departments and hospitals repetitive access to tissue diagnosis or test results is required and improves patient care. Turnaround time is the elapsed time from specimen collection to the reporting of the result. A LIS can shorten turnaround time by improving processing, transcription, distribution, billing, and affecting also other components of the examination. Productivity and financial management is increasingly important as healthcare resources become constrained. The LIS may optimize productivity of technologists, transcriptionists, and pathologists. The ability of the LIS to provide data at several different organizational levels for analysis by the user is also very important. The ability to extract data into formats that are easily imported into more sophisticated analysis programs (databases, spreadsheets) is also useful. Regulatory compliance: compliance with new official regulations and accreditation agencies requests for data may be better obtained by the use of information system extracting that information. Rapid collection of data enables the laboratory to perform quality assurance or various clinical-pathological correlation studies. Research support: the value of information systems in conducting medical research cannot be understated. The ability to analyze large quantities of data, collected over a prolonged period of time, is of great value. Particularly powerful are systems in which the laboratory system is linked with clinical information, so that outcome analysis can be performed. Hardware components include central processing unit, electronic storage of information, and ”dumb” or ”smart” terminals. Networks of various types connect computers with terminals, printers, modems, and other devices enabling integration of the whole pathology laboratory system. Software: The basic functionality of the software used to automate data and information handling in pathology includes registration, demographics, order entry, entry of results and the printing of reports. The anatomic pathology functions usually contain modules or subsections for surgical pathology, cytology, and autopsy pathology. Anatomic pathology reports are usually composed of text as narrative descriptions of clinical, gross, microscopic pathologic diagnosis and, in some cases, diagnostic clinical information. Coding mechanisms such as SNOMED (Systematized Nomenclature of Medicine) are used to subclassify or organize cases based upon the key words in their narrative descriptions. Databases in which diagnoses have been recorded may be searched by standardized code, 27 such as SNOMED or by natural language search to identify key words within the diagnosis. Depending on the accuracy of SNOMED coding, most objective comparisons will find that natural language searching techniques are most complete but more time consuming. INTERFACES An interface is an electronic or mechanical mechanism for data transfer between information systems. The most common interfaces are billing interface and an admissions-dischargetransfer between the hospital admitting system or hospital information system and the LIS. RESULT REPORTING Is accomplished by either printed reports or by electronic transmission of results to another LIS. The results are transmitted with a heading that contains information regarding the specimen and order so that the results may be linked to the patient. The results are sent as either a single component or a linked list of components that represent test codes as part of a battery or profile. Intangible benefits of this information system are: decreased turnaround time, improved report formats, increased access to results, reporting of work load of laboratory section, and many others. The information system is best implemented when physical plant and the layout of the network, training (a very important issue), and system support are well linked together. The pathologist assuming a leadership role in implementing the system is the most effective way to achieve desired results. EMERGING TECHOLOGIES Speech recognition allows computers to transform the spoken word into the text even in the form of continuous speech. This has been demonstrated to function also in pathology, as continuous speech systems permit dictation at rates equivalent to that obtained by a tape recorder. Shorter turnaround times and savings of secretarial staffing have been observed. Image management. Pathology, similar to radiology, depends on imaging technology to diagnose disease. Digital images can be now captured by different techniques and there is concentrated effort underway to move toward ”filmless” environment. The advantage of digitally stored material is that it consumes far less space, is more rapidly accessible and permanent and can be transmitted either within the own hospital or to remote viewing sites either for distant real-time consultation or educational purposes. Pathologist´s workstation integrates diverse clinical information from clinical, hospital, laboratory and radiology information system, so that with each specimen for study a complete clinical profile could be obtained, and at the same time access to hypertext modules, image archives of images, and online access to literature databases. These technologies and their use are rapidly expanding. 10. QUANTITATIVE METHODS (HISTOMETRY) Objective measurement of microscopic features has been advocated for decades as a method to make more reproducible and ”scientific” the practice of histopathology. It is only recently that technical advances in computing have rendered this procedure suitable for diagnostic and prognostic determinations in pathology. Traditionally the time-consuming measurements have been made from photographs, from projected images, or by use of a planimeter or eyepiece graticules followed by mathematical and statistical calculations. Most of the original contributions employing these techniques have been in the evaluation of non-neoplastic diseases of different organs including the human placenta. By means of histometry (stereology) data on the relative volume of different tissue components or surface area could be obtained (the mathematical principle was proposed as early as in 1846 by Delesse). Currently, semiautomatic or fully automated image analyzers are employed. At present, the method is also applied with increasing frequency to various aspects of tumor pathology, such as determination of DNA ploidy, proliferative index, nuclear grading and hormone receptor status. Needless to say, image analysis can be also applied to cytological preparations. Actually, a specimen composed of isolated cells in a clear background represents the technically ideal situation on which to employ this method. 11. MICROSCOPIC TECHNIQUE Speaking about the most convenient way of specimen study certain rules and recommendations should be carefully followed. Firstly, each specimen should be observed with a naked eye. This step helps assaying mainly the dimensions, shape, structure, composition and color of the given specimen. In a lesser degree this helps appreciate certain macroscopic properties or deviations from normal structure of the diseased tissue or organ (e.g. in a lymph node). Inserting the slide on the microscope stage it is very important to determine the location of the thin cover glass as this helps preventing of breaking the whole glass slide or damage the lens when installing and 29 using the high-power objective (x40) with the histological slide placed downwards on the microscope stage. During microscopic study it is principally important to proceed gradually from lowpower objective magnification (x4) through medium-power magnification (x10) to highpower magnification (x40). The low-power magnification offers the student a general introductory view of the whole specimen. It should be also learned, that the definitive diagnostic decision is sometimes made by means of the low-power magnification. Clean lenses of microscopic objectives and oculars as well as a correct illumination ( based on the so-called Koehler principle) is a prerequisite for successful and technically undisturbed microscopic observation. We suggest to make schematic drawings ( a general view and certain most important details) from all specimens in the time of practical exercises which together with descriptive remarks related to the theoretical description of each slide should help recall individual details important for the diagnosis during the time of final examination. B. PRACTICAL LESSONS IN HISTOPATHOLOGY 1. CELL NECROSIS OF RENAL TUBULES Necrosis is the sum of the morphologic changes that follow cell death in living tissues or organs. Necrosis is recognized histologically by changes of cell nuclei and cytoplasm. Nuclear destruction in necrotic cells includes pyknosis (nuclear shrinkage with increased density), karyolysis (dissolution) and karyorrhexis (fragmentation of nucleus). Eventually, the nucleus disappears completely. The cytoplasm of the necrotic cell is homogenized with distinctly increased eosinophilia and occasionally may be vacuolated. Cell necrosis should be distinguished from the apoptosis (distinctive pattern of individual cell death occuring in various physiological and pathological conditions). There are several types of necrosis. Coagulative necrosis is the most common form and occurs in almost all organs. Necrosis of the epithelium of the renal tubules also known as acute tubular necrosis (ATN) is associated with shock (ischemic ATN) or some chemicals (nephrotoxic ATN). The clinical consequence is sudden onset of anuria or severe oliguria and acute renal failure. Microscopically, there is no nuclear staining in the devitalized cells in coagulation necrosis, the cytoplasm is deeply eosinophilic (intensive pink-red), but the cell outlines are preserved. Ischemic ATN is characterized by focal tubular necrosis at multiple points along the nephron. Eosinophilic hyaline casts, as well as pigmented granular casts, are very common, particularly in distal tubules and collecting ducts. Other findings involve interstitial edema and accumulations of mononuclear leukocytes within dilated vasa recta. These changes may be reversible and during the recovery phase, epithelial regeneration is seen as the presence of flattened epithelial cells with hyperchromatic nuclei and mitotic figures. Toxic ATN is manifested by necrosis of proximal tubular epithelium and may be nonspecific in poisoning with the various chemical agents. Cell necrosis in ATN must be differentiated from anemic infarct that is caused by obstruction of the branch of the renal artery resulting in a grossly manifested area of coagulation necrosis. 2. CASEOUS NECROSIS OF THE LYMPH NODE Caseous necrosis is characteristic of tuberculous lesions and grossly appears as soft, 31 friable, cheesy map-like, yellow area. Tuberculosis is a chronic, communicable disease caused by Mycobacterium tuberculosis. Infection of lymph nodes is a consequence of spread of Koch bacilli to the draining one from the primary site. With the unaided eye, large homogeneous amorphous eosinophilic masses, i.e. caseificated tissues are seen to have replaced the originally presented lymphoid tissue. Microscopically, caseous necrosis is seen as amorphous eosinophilic material focally with small particles of blue-staining (basically with hematoxylin) nuclear debris. Necrotic tissue lacks any structure and may completely dominate the histologic picture. A special Ziehl-Neelsen stain would reveal tubercle bacilli in necrotic areas. Peripherally to the focuses of caseation there are noncaseating or caseating granulomas composed of epithelioid cells (modified macrophages with epithelial-like appearance) that form tubercle. Surrounding zone of fibroblasts and lymfocytes usually contains Langhans’ multinucleated giant cells. Numerous nuclei of the latter are arranged in a horseshoe pattern. This so-called specific granulation tissue may be visible only as a narrow border, or in some cases, caseous necrosis may be bordered by only a fibrous capsule. 3. LIQUEFACTION NECROSIS OF THE BRAIN Liquefaction necrosis is macroscopically characterized by softening and colliquation of the tissue. This type occurs when autolysis (enzymatic digestion by lysosomes of the dead cells themselves) and heterolysis (enzymatic digestion by lysosomes of immigrant leukocytes) prevail over protein denaturation of tissue constituents. Liquefaction necrosis occurs in the brain and in localized bacterial infections. This type of necrosis in the brain tissue named formerly encephalomalacia, contemporarily is termed infarction of the brain. Most commonly it is caused by a sudden reduction in the blood flow (vascular obstruction). Infarcted brain tissue in first 6 - 12 hours becomes anemic and by 48 hours, it turns softer and edematous. From 2 to 10 days, the brain becomes gelatinous and fraible. Later (from 10 days to 3 weeks) the tissue liquefies and eventually is removed, leaving a fluid-filled cavity. Histologically, infarct is initially associated with a polymorphonuclear leukocyte infiltration and is followed with progressive and prolonged infiltration by macrophages that digest the infarcted tissue. This first stage that shows brain softening is followed in the second stage by resorption of the destroyed myelin substance. Microscopical examination of the lesion with medium power reveals absence of the normal brain structure; rather, the tissue has spongy structure with the disappearance of neurons, glial cells and myelinated fibers. The area of ischemic necrosis reveals numerous round cells, the cytoplasm of which is filled with fat droplets that in paraffin sections are dissolved and thus, cytoplasm has a vacuolated appearance (foamy cells). These granular fatty cells have eccentrically located nuclei and are either phagocytic microglial cells or macrophages that have come in via blood vessels. Reactive glial reaction (astrocytosis) occurs about the second week of resolution and in the final state produces a fibrillary gliosis that surrounds the necrotic region. 4. ATROPHY OF THE LIVER (Brown atrophy) Atrophy refers to the decrease in size of an organ or cell by reduction in cell size (simple atrophy) and/or reduction in cell numbers (numerical atrophy). Simple atrophy is shrinkage in the size of cell due to loss of cell substance. Atrophic cells have diminished function but are not dead. They exhibit autophagy with a reduction in the number of cell organelles, and often a marked increase in the number of autophagic vacuoles (indigestible remnants of cell organelles and cytoplasmic materials). Components resisting digestion are converted to lipofuscin granules, which in sufficient numbers make the organ brown (brown atrophy). Macroscopically, liver is shrunken, brown and with wrinkled capsule. Microscopically, liver cells in acinocentral zones with increasing age tend to accumulate finely granular yellowish-brown pigment named lipofuscin. The pigment is best seen in histologic sections stained only with hematoxylin without a counterstain with eosin. Using high power, brown pigment cytoplasmic granules can be seen in liver cells surrounding the central vein of hepatic lobule. Lipofuscin granules should be differentiated from ironcontaining pigment hemosiderin that may be found chiefly in hepatocytes at the periphery of the liver lobule. The Prussian blue reaction colors the hemosiderin deep blue. 5. FATTY INFILTRATION OF THE HEART 33 In stromal fatty infiltration or ”fatty heart”, there is an increase in fat cells in the myocardium, such as is normally present to a small degree in the anterior portion of the right ventricle and occurs markedly in generalized obesity. Accumulation of fat cells in heart and pancreas is designated also as lipomatosis. The right ventricle is generally more severely affected than the left one. An increase of subepicardial fat is observed as finger-like projections extending between the muscle bundles. Stromal fatty infiltration should be differentiated from lipid accumulation in cells, especially in the heart muscle and liver cells that is called steatosis (fatty change). Microscopically, adult fat cells (round cells with optically clear cytoplasm and nuclei located peripherally) separate but do not damage the adjacent myocardial cells. The muscle fibers may be somewhat atrophic and incidentally show deposits of lipofuscin granules collections of which are present at the poles of the nuclei. 6. EXTRACELLULAR HYALINE CHANGES (Hyaline arteriolosclerosis of the kidney) Hyalin refers to any alteration within cells or in the extracellular space, which gives a homogeneous, glassy, pink appearance in routine histologic sections stained with hematoxylin and eosin. Hyalin is so a catchall word used to describe a variety of lesions of diverse origin that have a similar appearance when examined with the light microscope. Its name was derived from its resemblance to hyaline cartilage. Hyalin has various sites of localization and electron microscopical and immunohistochemical studies have shown that the structure and chemical composition of hyalin may be different in different sites and under different conditions. Principally two sorts of hyalin are recognized: intracellular and extracellular. Extracellular hyalin occurs most frequently in atherosclerosis, hyaline arteriolosclerosis, in damaged glomeruli and in old scars. Hyaline arteriolosclerosis of the kidney occurs typically in elderly patients, particularly those with mild hypertension and mild diabetes mellitus. The lesion is thought to reflect endothelial injury with subsequent leakage of plasma components into arteriolar walls, and smooth muscle synthesis of extracellular matrix. Microscopically, this kind of hyalin named also ”vascular hyalin” lies subintimally and leads to thickening of arteriolar walls. It is composed of plasma proteins, lipids, and basement membrane material. Hyalinization affects usually afferent arterioles with narrowing of their lumina. Decreased vascular perfusion leads to hyalinized thickening of some capillary loops and terminates in complete obliteration of a glomerulus. Cells of mesangium probably form the hyalin in glomerulus. 7. HYALINE DROPLETS IN THE RENAL TUBULES Hyaline droplets represent intracellular type of hyalin. This change does not have a macroscopically defined picture. Besides the kidney, Russell bodies in plasma cells and Mallory bodies in liver cells of alcoholics belong to this type of the hyalin. Hyaline droplets are protein particles that were reabsorbed from the lumen of the proximal renal tubules by process of heterophagocytosis and transiently are stored in phagolysosomes. Glomerular lesions, e.g. glomerulonephritis, frequently condition proteinuria as a basic disorder that gives rise to hyaline droplets of the renal tubules. Hyaline droplets are better visualized by PAS staining. Microscopically, protein hyaline droplets appear in the cytoplasm of tubular epithelial cells mostly in supranuclear regions. Proximal tubule cells reveal swelling due to infiltration of deep red (in hematoxylin-eosin sections) or purple red (in PAS sections) and somewhat refractile protein particles. The lumen contains granular precipitates of protein or hyaline casts. One rarely can see single epithelial cells, filled with protein-containing droplets, also in the lumen. 8. HYALINE CHANGES IN SPLENIC CAPSULE This type of hyalin belongs to the group of the extracellular hyalin. Macroscopically, hyaline depositions in splenic capsule can create two forms of lesions: either diffuse thickening resembling ”sugar icing” or local change in the form resembling drops of wax. The latter lesion was formerly designated by Latin term as ”perisplenitis cartilaginea guttata”. Histologically, the capsule of the spleen is focally thicker due to deposition of the extracellular hyalin. It is seen as a homogeneous substance stained pink-red in hematoxylin- 35 eosin sections. It is red in sections stained with van Gieson and blue when stained with trichrom. Between fibrils there are depositions of acid mucopolysaccharides and noncollagenous proteins that are visible with trichrom stain. Electron microscopically, hyalin maintains quarternary structure of collagen but the arrangement of fibrils is tangled. 9. FIBRINOID NECROSIS (DEGENERATION) IN RHEUMATOID NODULE Fibrinoid necrosis or degeneration develops after severe acute disturbance of vascular permeability with subsequent sudden leakage of blood plasma into the vessel and the surrounding connective tissue. Because of this, damaged tissues are either obscured or destroyed. Fibrinoid change cannot be seen by naked eye. It is observed mainly in rheumatic fever, rheumatoid arthritis, polyarteritis nodosa and malignant hypertension. Rheumatoid nodules are a part of the manifestation of the rheumatoid arthritis and are localized in the skin in the sites of pressure points and in the vicinity of joints. Nodules are firm, palpable subcutaneous masses, rarely exceeding 2 cm in diameter. Histologically, nodules have a central focus of fibrinoid necrosis surrounded by an intensive inflammatory infiltrate of palisade epithelioid histiocytes, external to which are numerous lymphocytes, macrophages, and plasma cells. Fibrinoid is mostly homogeneous red substance in hematoxylin-eosin sections, yellow in sections stained with van Gieson method, red in trichrom staining and slightly positive in Weigert stain for the fibrin component. The necrotic material is resistant to phagocytosis and therefore, the nodules are very persistent. Proliferation of small blood vessels may be remarkable in the early stage of formation of a rheumatoid nodule. 10. AMYLOIDOSIS OF THE KIDNEY Amyloid represents a heterogeneous group of pathologic fibrillar proteins that accumulate in various tissues and organs of the body. All these proteins are deposited in extracellular space. Depending on tissue of deposition, distribution and degree of involvement, amyloid may be asymptomatic and found only as an anatomic change, or may be life threatening. There are two major and several minor chemically distinct classes of amyloid fibrils. Two most important are AL (amyloid light chain protein) and AA (amyloid-associated protein). Amyloidosis is subdivided on clinical basis into systemic (generalized) and localized (tissue-specific) forms, and is further subclassified on the basis of predisposing conditions. Systemic amyloidosis is composed of AL-type of amyloid and is frequently associated with Bcell (lymphocyte) dyscrasias (primary amyloidosis), e.g. multiple myeloma. Another form of systemic amyloidosis named also secondary or reactive amyloidosis is associated with chronic inflammatory or tissue destructive processes, e.g. rheumatoid arthritis, so-called ”collagenoses”, bronchiectases and chronic osteomyelitis. This type of amyloidosis typically involves kidneys, spleen, liver, lymph nodes and adrenals. Microscopically, the amyloid is deposited primarily in glomeruli producing diffuse mesangial widening accompanied by uneven thickening of the basement membrane of the glomerular capillaries. Increasing depositions cause capillary narrowing and eventually lead to their obliteration. With progression of the disease, the glomeruli are flooded by confluent masses or broad ribbons of amyloid making them appear as large, amorphous and eosinophilic balls. The diagnosis of amyloidosis can be confirmed by examination of Congo red-stained sections. Under ordinary light, the dye imparts a pink-red color to amyloid deposits and under polarized light, the amyloid shows apple-green birefringence. The same process of amyloid accumulation occurs in the media of the arcuate arteries and afferent arterioles. Secondarily, amyloid is deposited in precapillary interstitial tissues and the tubular basement membranes. Many of the proximal convoluted tubules are dilated and contain casts, which have a hyaline appearance. 11. FATTY CHANGE OF THE LIVER (Fatty liver) The lipids of the liver are normally bound to cell components and are not seen by histological investigation. When fat appears in the form of droplets in the cytoplasm of the liver cells, the condition is known as steatosis or fatty change. This represents a normal constituent accumulating in excess and leading to an absolute increase in intracellular lipids. Pathogenesis of fatty liver is very complex and includes alcohol abuse, protein malnutrition, diabetes mellitus, obesity, toxins, and anoxia. The condition may result from defects in any one of the following mechanisms: excessive entry of free fatty acids into the liver, enhanced 37 fatty acids synthesis, decreased fatty acid oxidation, increased esterification of fatty acids to triglycerids, decreased apoprotein synthesis, and impaired lipoprotein secretion from the liver. Fatty change of the liver occurs in three forms: 1. peripheral; 2. central; and 3. diffuse. Macroscopically, fatty liver is enlarged, yellow and greasy. Microscopically, the extent of visible fat accumulation varies from minute droplets (microvesicular steatosis) scattered in the cytoplasm of a few hepatocytes to distension of the entire cytoplasm of most cells by coalesced droplets (macrovesicular steatosis). In the latter situation, the liver cell is scarcely recognizable as such and bears a resemblance to an adipocyte, the nucleus being squeezed into the rim of cytoplasm displaced to the periphery of the cell about the fat vacuole. Fat is dissolved in paraffin sections, therefore fat droplets are seen as optically clear spaces in hematoxylin-eosin staning. Examination of preparations stained with Sudan shows red positivity of the fat deposits. 12. VIRUS-INDUCED CELL INJURY (Molluscum contagiosum) Viruses as obligate intracellular parasites are the most common causes of human illnesses, yet most human viral infections are asymptomatic and go unrecognized. An example of virus-induced change with characteristic lesion is a common, self-limiting viral disease of the skin caused by a poxvirus named molluscum contagiosum. This disease is transmitted by direct contact. Macroscopically, lesions of molluscum contagiosum create firm, pruritic, pink to skin-colored, umbilicated papules, which are localized typically on the trunk or anogenital regions. Cheesy material containing diagnostic molluscum bodies can be expressed from central part of the lesions. Microscopically, it is a flask-shaped lesion produced by verrucous epidermal hyperplasia with pathognomic structures - molluscum bodies - that occur as large (up to 35 μm), ellipsoid, homogeneous, cytoplasmic inclusions in cells of the stratum granulosum and the stratum corneum of the epidermis. These inclusions representing aggregates of elementary bodies of the virus (numerous virions) are eosinophilic in the stratum granulosum and acquire red to pale blue hue in the stratum corneum. 13. DYSTROPHIC CALCIFICATIONS IN THE HEART Pathologic calcification implies the abnormal depositions of calcium salts in soft tissues. When the depositions occur in nonviable or dying tissues, it is known as dystrophic calcification. This type of calcification may occur in the absence of derangements in calcium metabolism and despite normal serum level of calcium. When calcium salts are deposited in living tissues, and calcium metabolism is abnormal and associated with hypercalcemia, the condition is known as metastatic calcification. Macroscopically the calcium salts appear as fine, white granules or clumps, and range from gritty, sandlike grains to firm, rock-hard material. Microscopically with the routine hematoxylin-eosin stain, the calcium salts have a basophilic (dark blue), amorphous or granular, sometimes clumped appearance. With time, heterotopic bone may be formed in the focus of calcification. On occasion, single necrotic cells may represent seed crystals and with progressive acquisition of outer layers, lamellated psammoma bodies may form. Extensive calcifications of the myocardium occur in necrosis together with hypercalcemia, for example in hyperparathyroidism. Calcified muscle fibers of myocardium are fragmented and stains blue with hematoxylin. The sections without decalcification are often disrupted when the calcium deposits are huge. 14. CHOLESTEROL CRYSTALS IN THE EPIDERMAL CYST Epithelial cysts filled with keratin and variable amounts of admixed, lipid-containing debris derived from sebaceous secretions are common lesions situated in the dermis or subcutaneous tissue. There are two types of these cysts referred to as keratinous cysts. The more common type is known as epidermal or epidermoid type. Although some of these cysts result from traumatic inclusion of epidermis, the majority probably arise from the upper (infundibular) portion of hair follicles. The second type of keratinous cyst is the pilar or trichilemmal type. It occurs almost exclusively in the scalp and arises from the deeper part of the hair follicle. Microscopically, epidermal cyst is lined by cornified epithelium, has a distinct granular layer, and contains lamellated keratin without calcification. Trichilemmal cyst is characterized by a trichilemmal type of keratinization, i.e., sudden keratinization without the formation of a granular layer. The cells adjacent to the contents of the cyst are large cells with abundant pale cytoplasm. The keratin inside the cyst is not lamellated (it appears as homogeneous 39 eosinophilic material) and focal calcification is frequent. When a keratinous cyst ruptures and the contents are released into the dermis, a considerable inflammatory and foreign-body reaction with numerous multinucleated giant cells results, forming a keratin granuloma. Depositions of needle-shaped, elongated cholesterol crystals seen in routine hematoxylin– eosin preparations as unstainable, optically clear structures (clefts) without internal details form a prominent part of keratin granuloma. Lipid-laden macrophages with foamy cytoplasm can be found in the contents of a cyst as well. 15. EXOGENOUS PIGMENTATION (Anthracosis of the lung) Pigments are naturally colored substances, which can be normal constituents of cells or they accumulate under pathological conditions. They are laid down in either diffuse or granular fashion. Pigments are traditionally divided into endogenous, and exogenous forms. Anthracosis refers to the storage of carbon particles in the lungs and regional lymph nodes. Virtually all urban dwellers inhale particulates of organic carbon generated by the burning of fossil fuels. These particles accumulate in alveolar macrophages (called anthracophages) and blacken the pulmonary tissue and lymph nodes. Although the gross appearance of lungs of persons with anthracosis may be alarming, the condition is entirely innocuous. Carbon particles reaching the alveoli are phagocytosed by type I pneumocytes or macrophages. The coal dust is insoluble, and phagocytic cells carry it into the lymphatic vessels. It is deposited mainly in the interstitial tissues of the lung. It is seen as dark black anthracotic pigment consisting of high-density small granules that are negative in Prussian blue stain and also in examination under polarized light. The host reaction consists occasionally of slight fibrosis or formation of perilymphatic connective tissue without cellular infiltration. 16. HEMOSIDEROSIS OF THE LIVER Hemosiderin is a product of the degradation of ferritin and is characterized as a hemoglobin-derived, iron-containing, golden-yellow or rusty-brown granular or crystalline pigment. It is formed when there is a local or systemic excess of iron. The most common causes of hemosiderosis of the liver (also termed secondary hemochromatosis) are the severe anemias associated with ineffective erythropoiesis and administration of transfusions. Grossly, liver is brown but in contradistinction to brown atrophy is of normal size. Microscopically, hemosiderosis of the liver is associated with depositions of hemosiderin granules in the cytoplasm of the liver cells and occasionally also in Kupffer cells. In contrast to lipofuscin granules, hemosiderin is found chiefly in hepatocytes at the periphery of liver lobules, especially near the bile canaliculus. The pigment appears yellowish-brown in hematoxylin-eosin sections, but the Prussian blue stain (named also Pearls reaction) colors the pigment deep blue. 17. SILICOSIS OF THE LUNG The pneumoconiosis is a pulmonary disease induced mainly by inorganic particulates. Silicosis is a pneumoconiosis caused by the inhalation of silicon dioxide (silica), usually in crystalline form as quartz. Particles of quartz dust ranging from 1 to 5 m in diameter are the most dangerous because they reach the peripheral zones, namely the smallest bronchioles and acini, and upon entering the terminal air spaces they are ingested by alveolar macrophages. Quartz can cause direct injury to tissue and cell membranes. Moreover, silica triggers macrophages to release products mediating an inflammatory response and initiating fibroblast proliferation and collagen deposition. The fibrous nodules start as small lesions in the upper portions of lungs, but grow larger and more diffuse as the disease progresses. Coalescence of nodules forms large areas of dense scars and concomitant blackening of coal dust is often present. Microscopically, nodules have a characteristic whorled appearance, with concentrically arranged hyalinized (acellular) collagen that forms the largest part of the nodule. At the periphery there are aggregates of mononuclear cells, mostly lymphocytes, and fibroblasts. Histiocytes containing carbon (coal dust) can be seen mainly at the periphery of the silicotic nodule. In silicotic nodule there are very few blood vessels. The silica particles are colorless and not visible in routine hematoxylin-eosin staining but can be detected readily under 41 polarized light. The cracks in the tissue are caused by shrinkage during processing. 18. HYPERTROPHY OF THE HEART Hypertrophy is an increase in the size of a cell accompanied by an augmented functional capacity and increased number of organelles (e.g. myofilaments). With such change, there is an increase in the size of the organ. Hypertrophy can be physiologic or pathologic. The striated muscle cells in both the heart and skeletal muscles are most capable of hypertrophy, perhaps because they cannot adapt to increased metabolic demands by mitotic division and formation of more cells to share the work. In cardiac hypertrophy weight of heart may reach more than 500 - 600 gm instead of normal weight of 300 - 350 gm. The examples of adaptive hypertrophy involve patients with hypertension (high blood pressure) and with diseased cardiac valves. The DNA content of heart muscle cells in myocardial hypertrophy depends on the age. In adults, tetraploidy predominates and with increasing cardiac load, polyploidy increases. Microscopically, myocardial hypertrophy can be appreciated by comparing the width of the muscle fibers, the size and shape of their nuclei, and the number of nuclei per unit area. In cardiac hypertrophy, muscle fibers are thickened twofold to threefold over normal, the number of nuclei per unit area is decreased and the nuclei, mirroring an increase in DNA content, are enlarged, hyperchromatic and misshapen (angulated). In cross-sectioned sarcoplasm one can see thickened myofilaments that are increased in number. 19. CHRONIC PASSIVE CONGESTION OF THE LIVER (”Nutmeg liver”) Congestion, or passive hyperemia, refers to the engorgement of an organ with venous blood. In chronic heart failure, when the right side of the heart fails to maintain its output, the inferior vena cava and hepatic veins become congested. Grossly, the liver is enlarged and dark red. On the cut surface, the contrast between red-blue congested centers rimmed by tanbrown, and sometimes fatty parenchyma of peripheral portions of the lobules produces the ”nutmeg” pattern. When marked congestion of the liver has been present for some time, congestion also involves intermediate zones of lobules and the peripheral zones are only affected where lobules adjoin each other. Thus, congested bands of tissue are formed which connect one liver lobule with another and lead to a reversal of the previous liver pattern so that the periportal field is in the middle of a red ring of hyperemia. Microscopically, the central vein and the sinosoids of centrilobular regions become dilated. The increased venous pressure and hypoxia lead to atrophy of the centrilobular hepatocytes, whereas the surrounding hepatocytes, suffering from less severe hypoxia, develop fatty change. With ongoing and more pronounced congestion, the periportal fields are seen to be at the centers of communicating and coalescing congested areas that contain greatly dilated sinusoids and disappearing liver cells. In extreme cases with severe cardiac failure, frank hemorrhagic necroses of the central hepatocytes are conspicuous. 20. CHRONIC PASSIVE CONGESTION OF THE LUNG (Brown induration of lung) Chronic passive congestion of the lungs results from an impediment to the exit of blood from the lungs (e.g. mitral stenosis or chronic failure of the left ventricle). As a consequence, the pressure in the alveolar capillaries is increased (postcapillary hypertension), and these vessels become engorged with blood. Grossly, the lungs are heavy, firm and brown. Changes such as these not only impair normal respiratory function but also predispose to infection. Thus, bronchopneumonia often terminates long-term congestive heart failure. Microscopically, the raised blood pressure in the pulmonary capillaries causes them to become dilated and tortuous. The alveolar septa are widened both by dilatation of alveolar capillaries and by edema fluid that collects within the interstitial space of alveolar septa. Red cells leak into the alveolar lumens, and macrophages also present in the alveoli ingest them. Some of the macrophages are very large and distended with hemosiderin derived from broken-down hemoglobin of the phagocytized erythrocytes. These macrophages containing hemosiderin are called siderophages or ”heart failure cells”. The Prussian blue reaction shows that the pigment contains iron. The siderophages tend to congregate around the respiratory bronchioles and may release iron-containing salts which are then deposited in the connective tissue of the lung. In time, the edematous septa become fibrotic and, together with the hemosiderin pigmentation, constitute the basis for the designation brown induration. The van 43 Gieson stain demonstrates an intensely red-stained network of fibers. The long-standing congestion and pulmonary hypertension may cause progressive thickening of the walls of the pulmonary arteries and arterioles. 21. THROMBOSIS (Mural thrombosis in aorta) Thrombosis is defined as the intravital formation of a clotted mass of blood constituents within the noninterrupted cardiovascular system. There are three predisposing factors that may result in thrombus formation: 1) injury to endothelium, 2) alterations in normal blood flow, and 3) changes in the blood constituents (hypercoagulability). In the heart chambers and aorta, because of rapid bypassing flow, thrombi are nonocclusive and are designated as mural. They are soft, friable, and grayish red or dark red, with fine alternating bands of yellowish layers, the so-called lines of Zahn. These rib-like projections of platelets seen on the surface of the thrombus give it a rippled appearance crosswise to the direction of blood flow like the pattern of a wind-swept sand dune or a sandbank at the bottom of a river. Microscopically, thrombus adheres to the vessel wall and has a typical appearance. Conglutinated blood platelets are built up into a coral-like laminated scaffold. Under high magnification, the platelets appear as finely granular, anuclear usually fused particles 1-4 μm in diameter. Fibrin seen as light pink network surrounds and also lies between the columns of platelets, giving an appearance like that of a reinforced steel building. Leukocytes are enmeshed in the fibrin and accumulate like mantles around the bands of blood platelets. Trapped collections or masses of erythrocytes lie throughout the thrombus. 22. WHITE INFARCT OF THE KIDNEY An infarct is a localized area of ischemic necrosis in an organ or tissue, resulting most often from sudden occlusion of its arterial supply. Infarcts are classified on the basis of their color as hemorrhagic or red and ischemic known as pale or white. White infarcts occur in solid organs with end arteries (those having few anastomoses) such as kidneys, heart and spleen. White infarct of kidney is most frequently caused by embolic obstruction of a branch of the renal artery resulting in a wedge-shaped area of coagulation necrosis with the base at the cortical surface and the apex pointing toward the medulla. On gross examination, 1 to 2 days after initial hyperemia, the pale infarct becomes yellow, dry and sharply delineated. Examination of the section with a scanning lens reveals a pale red, wedge-shaped area, surrounded by bluish, highly cellular zone outside of which there is a thin red rim. Histologically, the central portion of the wedge-shaped area reveals typical signs of coagulative necrosis: there is no nuclear staining and the cytoplasm is deeply eosinophilic. On the whole, early infarcts will still show the faint outlines of tubules and glomeruli. Polymorphonuclear leukocytes accumulate in the peripheral zone and they present with signs of nuclear disruption (pyknosis, karyorrhexis, lysis or finely scattered nuclear debris). Surrounding this cellular area, there is a zone of reactive hyperemia. It is remarkable that often a subcapsular strip of preserved parenchyma is without signs of necrosis because it receives its blood supply from the capsular vessels. 23. RED INFARCT OF THE LUNG Red or hemorrhagic infarct is encountered with venous occlusion, in loose tissues or in tissues having a double or anastomotic circulation, and in tissues previously congested. Hemorrhagic infarct of lung denotes focal necrosis and hemorrhage of lung tissue following embolic occlusion of a middle-sized branch of the pulmonary artery in the presence of passive hyperemia in the bronchial circulation which inadequately compensates for the loss of supply from the plugged branch of pulmonary artery. This circumstance is often found in congestive heart failure. Stasis and increased pulmonary venous pressure is usually also present. Grossly, the infarct of lung is a dark red hemorrhagic, wedge-shaped, raised mass, with its ”base” on the pleural surface. Often the apposed pleura is covered with a fibrinous exudate. Naked eye inspection of a histologic section usually reveals a wedge-shaped, red and homogeneous lesion. The embolic occlusion of the nutrient branch of the pulmonary artery cannot be always seen. Microscopically, the diagnostic feature is the ischemic necrosis of the lung substance within the area of hemorrhage, affecting the alveolar walls, bronchioles, and vessels. The lesion discloses monotonous histologic picture: the alveolar spaces are filled with densely packed erythrocytes that are seen in older infarcts as shadow forms or are disintegrated. The alveolar septa are necrotic (without any stainable nuclei), and can scarcely be distinguished 45 from the contents of the alveoli. The capillaries are full of blood but endothelial and alveolar epithelial cells cannot be detected. 24. PULMONARY EDEMA Edema is an abnormal accumulation of fluid within interstitial spaces or body cavities. Edema may be localized or systemic (generalized). Major clinical causes of systemic edema are congestive heart failure, renal diseases and sodium retention, and diffuse hepatic diseases with decreased synthesis of serum proteins. Pulmonary edema can result from hemodynamic disturbances or from direct increase in capillary permeability, owing to microvascular injury. The most common hemodynamic mechanism is associated with left ventricular failure that causes increase in the blood pressure abruptly in the pulmonary veins and in the capillaries in the walls of the alveoli in the lungs. Pulmonary edema may be interstitial or alveolar. The former represents the earliest phase and when the fluid can no longer be contained in the interstitial space, it spills into the alveoli (condition termed alveolar edema). Macroscopically, the lungs are heavy and wet, and in far-advanced cases assume a rubbery gelatinous consistency. Sectioning of the parenchyma permits the free escape of frothy, pink watery fluid representing a mixture of edema fluid and air bubbles. Histologically, the alveolar capillaries are engorged and alveoli are filled with homogeneous eosinophilic material, which has leaked from the congested capillaries. A transsudate of this type is usually cell-free but there may be present a few solitary, exfoliated alveolar epithelial cells, i.e. alveolar macrophages. In some places, alveolar fluid has been lost and thus, the presence of empty spaces has resulted (air bubbles). 25. ACUTE SEROUS INFLAMMATION OF SMALL INTESTINE Inflammation is the reaction of vascularized living tissue to local injury. Inflammation consists of a series of complex reactions by vascular and connective tissue elements to various damaging agents. Major events in the acute phase of inflammation involve changes in vascular flow and caliber, increased vascular permeability, and leukocyte exudation. In serous inflammation, protein-rich thin fluid leaks from the blood vessels with a relatively low cellular content. When mucus hypersecretion accompanies serous inflammation of a mucous membrane, the appearance is described as catarrhal. Macroscopically, small bowel mucosa appears congested (bluish red) due to vascular dilatation and edematous. Microscopically, most bacterial infections exhibit a general nonspecific pattern: damage of the surface epithelium occasionally with desquamation of the isolated cells, decreased epithelial cell maturation, and an increased mitotic rate in mucosal crypts (”regenerative change”). Goblet cells may display hypersecretion. Blood vessels in edematous lamina propria are hyperemic. Mild cases show increased numbers of plasma cells, and some degree of neutrophilic infiltration into the lamina propria and epithelial layer. More severe cases are accompanied by a more pronounced neutrophilic response and villous atrophy but a decreased number of plasma cells. 26. CHRONIC INFLAMMATION OF THE NASAL CAVITIES Inflammatory diseases are the most common disorders of the nasal cavity and paranasal sinuses, and are named rhinitis and sinusitis, respectively. As usual, they are associated with infection (mainly of viral origin but often complicated by superimposed bacterial agents) and allergy. Chronic inflammation may follow acute inflammation, may result from repeated bouts of acute inflammation, or most commonly it begins insidiously as a primary chronic inflammation. Often a deviated nasal septum is a contributory factor. Chronic rhinitis or sinusitis is characterized by mucosal thickening and increased consistency with production of nasal polyps. They are not true neoplasms, but rather focal inflammatory swellings of mucosa of the nose or paranasal sinuses. They are divided into allergic and nonallergic types. Macroscopically, polyps appear as sessile or pedunculated, smooth, pale, movable, rounded tumors protruding into the airways. Histologically, polyps are lined externally by respiratory epihelium sometimes undergoing squamous metaplasia and frequently resting on a thick basement membrane. They often contain hyperplastic or cystic mucous glands within a loose mucoid stroma. Persistent hyperemia of stromal blood vessels is observed as well. Inflammatory infiltrate consists of a variety of cells including lymphocytes, plasma cells (sometimes with eosinophilic cytoplasmic inclusions called Russell bodies), eosinophils (prominent in allergic polyps), neutrophils and mast cells. 47 27. ACUTE PURULENT (SUPPURATIVE) MENINGITIS The term meningitis usually refers to inflammation in subarachnoid space involving the arachnoid and pia mater, i.e. leptomeningitis. However, under certain circumstances it may involve predominantly the dura mater (pachymengitis) usually being the consequence of contiguous infection, such as otitis media or mastoiditis. Leptomeningitis is frequently a result of blood-borne infection, but it can arise from direct spread from the skull bones, or from penetrating wounds as well. In acute purulent leptomeningitis, pyogenic organisms (Neisseria meningitidis, Streptococcus pneumoniae, etc.) spread throughout the subarachnoidal space. This may happen very rapidly and the persons may die within a few hours. Macroscopically, the meningeal vessels are engorged and stand out prominently. The normally clear cerebrospinal fluid is cloudy and sometimes is frankly purulent. The inflammatory exudate collects in the subarachnoid space and the location of the exudation varies dependent on etiologic agents. Microscopic examination with low power reveals a dense cellular infiltrate in the leptomeninges. Higher magnification shows that polymorphonuclear leukocytes fill the entire subarachnoidal space. They are found predominantly around the leptomeningeal blood vessels in less severe cases. Cellular infiltrates are focally intermingled with fibrin strands. In fulminant cases, the inflammation may extend into the substance of brain (focal encephalitis) by means of inflamed leptomeningeal veins. In untreated meningitis, Gram stain reveals numbers of causative microorganisms, although they are frequently not present in treated cases. 28. ACUTE PURULENT APPENDICITIS Acute appendicitis is an inflammatory disease of the wall of the vermiform appendix that often results in transmural necrosis and perforation, with subsequent peritonitis. It is often associated with obstruction, usually in the form of fecalith. However, no obstruction is demonstrated in significant minority of cases, and the factor precipitating the disease remains unknown. Macroscopically, resected appendix is congested, tense, and covered by fibrinous exudate. The lumen often contains purulent material, and a fecalith may be evident. At the earliest stages, only a scant neutrophils may be found in the lamina propria and the inflammation proceeds with a focal suppurative lesion at the bottom of a crypt. Following this, the surface epithelium is breached and the mucosa is destroyed by focal inflammatory exudation of fibrin and leukocytes. Later on, the necrotic tissue may slough and an ulcer forms (acute ulcerative appendicitis). The acute inflammatory process tends to spread along the muscular and serous coats, particularly if the lumen is obstructed. This form of acute appendicitis is named phlegmonous. The mucosa is largely destroyed in advanced states, only a few remnants of the glands remaining. The blood vessels are greatly dilated and the whole of the appendiceal wall is infiltrated with polymorphonuclear leukocytes. As the inflammatory process is getting worse, there is abscess formation within the wall. There is also reactive exudation of fibrin and leukocytes over the peritoneal aspect. Eventually, further appendiceal compromise may lead to necrosis of the wall, followed by perforation and subsequent purulent peritonitis. 29. CHRONIC GRANULOMATOUS INFLAMMATION (Tuberculosis of the lung) Granulomatous inflammation is a distinctive pattern of chronic inflammatory reaction and is characterized by formation of granulomas. The classic example of granulomatous disease is tuberculosis, but sarcoidosis, syphilis, cat-scratch disease, leprosy, lymphogranuloma inguinale, brucellosis, deep fungal infections, beryliosis and reactions to a foreign body, all evoke this pattern. Tuberculosis of the lung may be primary or secondary. Primary form occurs in individuals lacking previous contact with tubercle bacilli. The route of infection is generally by inhalation of droplets from other individuals suffering from the disease. The secondary tuberculosis denotes active infection in a previously sensitised individual. Most cases represent reactivation of dormant bacilli from primary lesions. Secondary tuberculosis is generally found in the apices of the lungs. These lesions may progress to cavitary fibrocaseous tuberculosis, tuberculous bronchopneumonia, or miliary tuberculosis. Histologically, coalescent granulomas are present in pulmonary parenchyma. Granulomas are small (0,5 – 2 mm) collections of modified macrophages called ”epithelioid 49 cells” (with epithelial-like appearance), usually rimmed by lymphocytes. They have abundant, pink, plump cytoplasm with indistinct cell boundaries, often appearing to merge into one another. Epithelioid cells may coalesce and fuse to form multinucleate giant cells known as Langhans’ cells. Their nuclei are arranged around the cell periphery creating a horseshoe pattern. The granulomas caused by Mycobacterium tuberculosis are named tubercles. The typical tubercle consists of a necrotic center (caseification), a zone of epithelioid cells, Langhans’ giant cells, and a more or less well-marked outer margin of lymphocytes and a few plasma cells. Caseous necrosis seen as eosinophilic, homogeneously and finely granular area without recognizable remnants or cell outlines of the original tissue may sometimes completely dominate the picture and specific granulation tissue (epithelioid cells, Langhans’ cells and lymphocytes) is visible only as a narrow border. Tubercle bacilli are very difficult to stain and they can be detected as red rods only in sections stained by the Ziehl-Neelsen method for staining acid-fast bacilli. 30. CHRONIC GRANULOMATOUS INFLAMMATION (Sarcoidosis of lymph node) Sarcoidosis is a granulomatous noncaseating inflammatory disease of unknown etiology which affects many tissues, including lymph nodes. These are involved in almost all cases, particularly hilar and mediastinal nodes, but any other node in the body may be affected. Macroscopically, lymph nodes are considerably enlarged, discrete, and sometimes lobulated or calcified. Microscopically, the normal architecture of the node may be largely destroyed, with some blue-staining lymphoid tissue surviving mostly beneath the capsule and between the round sarcoid granulomas. Sarcoid epithelioid cell granulomas are numerous and in part confluent. In contrast to tuberculosis, there is no caseation and granulomas tend to fibrose from the periphery toward the center. Higher magnification shows epithelioid cells having plump eosinophilic cytoplasm with vesicular nuclei. Several multinucleated giant cells of Langhans’ type are also present. Some sarcoid granulomas contain intensively basophilic calcified and laminated Schaumann bodies, and occasionally also star-shaped inclusions called asteroid bodies enclosed within giant cells. None of these structures are specific for sarcoidosis because they can be found in other granulomatous diseases (e.g. berylliosis). The capsule of the lymph node becomes frequently somewhat fibrotic. 31. GRANULATION TISSUE (Inflammation in the (sub)chronic stages, connective tissue repair) In the (sub)chronic stages of the inflammation and connective tissue repair, proliferative changes may predominate. They are associated with proliferation of fibroblasts and formation of new small blood vessels termed neovascularization or angiogenesis. These two components are the main histologic constituent elements of granulation tissue. Macroscopically, the term ”granulation tissue” is derived from its pink, soft granular appearance on the base of a skin ulcer; when the repair process is observed, the capillary loops are visible and impart a granular texture. Such a name is less appropriate for an internal repair, but is used despite this. The formation of granulation tissue is a regulated process involving a number of events, including growth of new capillaries, fibrogenesis, and involution during maturation of the scar. Granulation tissue must not be confused with a granuloma (an aggregate of epithelioid histiocytes). Microscopically, new vessels originate by budding or sprouting of pre-existing vessels. These new capillaries have leaky interendothelial junctions, allowing the passage of proteins and erythrocytes into the extravascular space. Therefore, new granulation tissue is often edematous. In newly developing granulation tissue, fibroblasts proliferate and appear as large cells having plump, sometimes basophilic cytoplasm and hyperchromatic nuclei. They produce collagen which is the basic component of a scar. Some of the large fibroblasts acquire features of smooth muscle cells and thus, they are named myofibroblasts. These cells are responsible for wound contraction. Besides fibroblasts and capillaries, macrophages, neutrophils, lymphocytes and plasma cells are almost always present in granulation tissue. Mast cells and eosinophils may sometimes be seen as well. In the course of the healing process, many of the blood vessels undergo thrombosis and degeneration, and are digested by macrophages. The end result of granulation tissue is a scar composed of inactive-looking, spindle-shaped fibrocytes, dense collagen, fragments of neoformed elastic tissue, extracellular matrix, and relatively few vessels. 32. ORGANIZED AND RECANALIZED THROMBUS 51 A newly developed thrombus has potency for several modes of outcome. It may 1) propagate and cause obstruction of some vessels, 2) give rise to an embolus, 3) be removed by fibrinolytic action, or 4) become organized and possibly recanalized. The process of organization converts the thrombus into a firm and grayish white connective tissue, acquiring somewhat spongy appearance if prominently vascularized. Recanalization is the process by which new lumina lined by endothelial cells form in an organized thrombus. Microscopically, the appearance of recanalization of an arterial thrombus depends on the age, mass of the thrombus and the degree of recanalization. In the beginning of thrombus organization, phagocytic and proteolytic activity of the macrophages and leukocytes decompose fragments of fibrin, red cells and platelets. Concurrently fibroblasts and capillaries proliferate and invade the base of thrombus where it is attached to the underlying vessel wall. Thus, the lumen is occupied by a mass which is penetrated by thin-walled and widely patent blood vessels. Some of them may differentiate into small veins or arteries. The vascular channels may anastomose to produce communications that traverse the thrombus and through which the blood flow may at least in part be re-established. The black-brownish granules found in the organizing tissue are intracellular broken-down products of hemoglobin, i.e. hemosiderin. Special stains would show abundant reticulin but few mature collagen fibers. The wall of thrombotic artery demonstrates atherosclerotic changes. potiaľ 33. CHRONIC GRANULOMATOUS INFLAMMATION AROUND FOREIGN BODIES (Foreign body granuloma) Granulomatous inflammation is typical tissue response elicited by miscellaneous injury. The hallmark of this distinctive pattern of chronic inflammation is the presence of small collections of epithelioid cells (i.e. modified macrophages) referred to as granulomas. Epithelioid cells may transform into multinucleated giant cells, the presence of which is another feature of the granulomatous inflammation. So-called foreign body-type giant cells are characteristically seen in relation to particulate foreign-body indigestible material (talc crystals, suture material from the surgical incision, miscellaneous exogenous material – wood, metal, oil or paraffin). Microscopically, the nodules of chronic granulomatous inflammation around foreign bodies basically consist of granulation tissue with dilated thin-walled blood vessels, lymphocytes and plasma cells, and elongated fibroblasts. Occasionally, polymorphonuclear leukocytes predominate. The most notable feature, however, is the presence of multinucleated giant cells of foreign body-type. They are large cells formed by the cytoplasmic fusion of macrophages with numerous (up to 50–100) separate nuclei randomly scattered throughout their cytoplasm. Typically, they contain fragments of foreign material or conglomerate around a foreign body. Foreign body granuloma may have a zone of scarring process at the periphery. 34. SQUAMOUS METAPLASIA OF CYLINDRICAL EPITHELIUM Metaplasia refers to a reversible transformation of one mature differentiated cell type (epithelial or mesenchymal) into another. It often represents a response to persistent stress or injury. This process can be thought of as an adaptive substitution of cells more sensitive to stress by cell types better able to withstand the adverse environment. It should be emphasized that metaplasia is not necessarily a harmless process and, in most circumstances, represents an undesirable change. The most common adaptive mataplasia is the replacement of a glandular epithelium by a squamous one. Columnar lining cells commited to differentiated functions, such as mucus production, assume a simpler form providing more protection against pernicious chemical action or the effects of chronic inflammation. A very common example of the above-mentioned process is the substitution of the normal cylindrical epithelium of the cervical mucosa (or of an endocervical polyp) by metaplastic squamous epithelium. Endocervical polyp is a focal, hyperplastic or inflammatory protrusion of endocervical fold and appear as a single, pedunculated or sessile, smooth or lobulated outgrowth originating in the mucus-secreting columnar epithelium of the endocervix. Histologically, endocervical polyps are composed of loose fibromyxomatous stroma containing dilated, mucus-secreting endocervical glands. Blood vessels are usually thickwalled and may be prominent. The lesion is frequently associated with acute or chronic inflammation and squamous metaplasia of varying degrees. The latter process entails first the proliferation of endocervical basal ”reserve cells” and then the differentiation of these cells into squamous cells rather than mucin-producing cells. Initially, the reserve cells do not have squamous characteristics; rather, they appear as cuboidal cells with round nuclei growing beneath the mucinous epithelium. After the reserve cells proliferate and stratify, they differentiate into squamous cells that initially have only slightly increased amounts of 53 cytoplasm (immature squamous metaplasia). Later the cells may fully mature to glycogencontaining squamous cells indistinguishable from the superficial cells of the exocervix, progressively lift up and finally push off the cylindrical epithelium. 35. PSEUDOTUMOR (Epidermoid cyst) Pseudotumor is a pathologic lesion that grossly or clinically bears some resemblance to a genuine tumor but its real nature is nonneoplastic. From the biological point of view, all pseudotumors are benign. Many miscellaneous pathological changes (some developmental anomalies, hypertrophy, hyperplasia, cysts, some pathological material and inflammation) are included in this category of pseudotumors. The cyst is a cavity that arises from dilatation of a pre-existing structure and is generally lined by epithelium. Epidermoid (epidermal) cysts are a common type of keratinous cysts (cysts filled with keratin). They are situated in the dermis or subcutaneous tissue and appear spontaneously as a rule (probably arising from the upper portion of hair follicles) but may also originate from epidermis transplanted into the deeper layers of the skin by trauma. They grow slowly to reach several cm in diameter, elevating the overlying skin. The second type of keratinous cyst is pillar or trichilemmal cyst. Epidermal cysts have a wall composed of true epidermis, as seen on the skin surface and in the infundibulum of hair follicles. In young cysts, several layers of squamous and granular cells can usually be recognized. In older epidermal cysts, the wall often is markedly atrophic and may consist of only one or two rows of greatly flattened cells. The cyst is filled with horny keratinous material arranged in laminated layers without calcifications. A considerable foreign-body reaction results when the wall of a cyst ruptures, thus forming a keratin granuloma. 36. PRENEOPLASTIC DISORDER (Cervical dysplasia) Dysplasia means deranged development: however, in common usage it is applied to either epithelial or mesenchymal cells, principally to former, that have undergone proliferation and atypical cytologic alterations involving cell size, shape, and organisation. In the case of cervical dysplasia it is but one example of precancerous lesions in two types of local lining epithelia. Occasionally, this change may be reversible and, with removal of the putative inciting causes, the epithelium may revert to normal. However, after some time intervals (usually expressed in years) these lesions may gradually intensify and convert to preinvasive and finally to invasive neoplastic disease. The cervical location is one of the most frequent sites of preneoplastic epithelial changes. After puberty, or later, due to physiological changes in the position of the cervical squamo-columnar junction the local, metaplastic squamous epithelium exposed to different types of irritation (e.g. low pH, infectious agents, etc.) becomes labile and this area is called ”transformation zone”. Gradually, a spectrum of various microscopical changes develops within the superficial cervical epithelium or in the same epithelium replacing cylindrical epithelium of underlying cervical mucous glands. The width of the epithelium (acanthosis) and the basal cell activity is individually increased. The superficial zone of the squamous epithelium may show parakeratosis and hyperkeratosis (not present in the normal, noncornifying epithelium). The individual epithelial cells may become dysplastic (atypical cells) with abnormal nuclei. Individual cells may cornify and mitotic figures may be found also higher than in the basal cell layer. There is a disordered maturation of the cells as they proceed to the superficial layers. The increased proliferative activity produces greater amounts of DNA causing more intense basophilia of the nuclei. A large part of cellular changes: hyper- and parakeratosis, characteristic perinuclear vacuolisation (= koilocytosis), dyskeratosis, bi- or multinucleation and papillomatosis of the epithelium may be attributed according to the results of modern molecular biology techniques to human papilloma virus (HPV) infection. Due to progression of the disease and increase in histological severity these epithelial preneoplastic (precancerous) changes reach individual degree of severity even in different parts of the same specimen. Therefore, dysplasia is subdivided into mild, moderate, and severe, depending on the proportion of the thickness of squamous epithelium involved by atypical cells. Grade 1 represents less than one-third involvement of the thickness of the epithelium (basal third). Grade 2 represents involvement of one-third to two thirds, and Grade 3 two thirds to almost full thickness, leaving only a thin, supermost layer of nontransformed cells. For the same lesion in many Western countries instead of the term ”dysplasia” the term ”Cervical intraepithelial neoplasia” (CIN) is widely used. Such morphological diagnosis can be made not only in the biopsy material, but also cytologically. As already shown in the Introduction, cytology is a simple, relatively safe, and non-invasive method of detecting precancerous changes in the cervix uteri introduced by Papanicolaou, which can be used as a screening programme in large groups of population at risk. The next 55 step in the progression of a severe dysplastic lesion (Grade 3), which has reached already true neoplastic character, is called ”Carcinoma in situ” (CIS) or non-invasive (preinvasive) carcinoma (see the next paragraph). 37. CARCINOMA IN SITU (Intraductal carcinoma of the breast) The term ”Carcinoma in situ” (CIS) refers to an epithelial neoplasm, containing all cellular features associated with malignancy, which has not yet invaded through the epithelial basement membrane separating it from potential routes of metastasis – blood and lymphatic vessels – and thus having no signs of invasive growth. The phase of ”in-situ” growth may last for several years before invasion commences. Microscopical appearances of non-invasive carcinoma of the breast are variable. The intraductal pattern of growth may be papillary, cribriform, or so-called comedocarcinoma. In cribriform carcinoma the tumor cells with variable-sized nuclei fill the large and mediumsized secretory ducts, producing multiple small lumina, giving the intraductally growing tumor a characteristic sieve-like appearance. In comedo-carcinoma the dilated ducts are also distended by the solid growth of pleomorphic carcinoma cells, with frequent mitotic figures, centrally undergoing necrosis in many places. Micro-calcifications and stromal reaction are frequent supplementary findings. The intraductal papillary carcinoma occurs mostly in postmenopausal women: papillary neoplastic structures fill the distended ducts. Another example of an in-situ pattern of neoplastic growth in the breast is the carcinoma lobulare in situ (CLIS), developing characteristically from breast lobule epithelia. Each untreated case of CIS carries the risk of progression to an invasive carcinoma. 38. METASTASIS OF CARCINOMA IN THE LYMPH NODE Metastases are tumor implants discontinuous with the primary tumors. The invasiveness of cancers permits them to penetrate into the blood vessels, lymphatics, and body cavities, providing the opportunity for spread. Discovery of atypical (neoplastic) epithelial tissue in a lymph node indicates metastatic carcinoma. The appearance of lymph node metastasis can have diagnostic (the first clinical manifestation of an occult carcinoma), prognostic (i.e. bad sign), and therapeutic significance. Transport through the lymphatics is the commonest pathway for the initial dissemination of carcinomas. The spread of sarcomas may also be similar. The lymph nodes are invaded by groups (islands) of metastatic carcinoma cells lying in distended sinuses or infiltrating diffusely a part or the whole lymph node. Floating groups of neoplastic cells may also be present in lymphatic vessels leaving or entering the nodal hilus. 39. CHARACTERISTICS OF MALIGNANT NEOPLASMS (Parenchyma and stroma, anaplasia, and atypical mitoses) Most of malignant neoplasms grow in a solid manner. Only a small number of tumors has cystic appearance on its surface as well as on cut section. All tumors consist of neoplastic cells and stroma, embedding and supporting the ”parenchymal” neoplastic cells. The neoplastic cells reproduce to a variable extent the growth and structural pattern and synthetic activity of the parent cell of origin. Depending on its functional resemblance to the parent tissue, it continues to synthetize and secrete cell products, such as bile, keratin, mucin, melanin pigment, hormones etc. The presence of these products is helpful in recognizing the origin (histogenesis) of the tumor cells. The cells are growing in various forms, forming solid sheets, nests, islands, glandular or trabecular patterns or – after total loss of cellular cohesivity – separately (individually), surrounded by the more or less actively proliferating stroma. Cytologically, the neoplastic cells differ widely in their morphological properties, such as the number of cells per unit, the size and shape of their cytoplasm, variability of individual nuclei and nucleoli. Frequently, the cytoplasmic/nuclear ratio is changed. The nuclei are not only irregularly larger but also have thickened nuclear membrane with indentations of their outline. The chromatin is coarse and deeply stained. Some of the neoplastic cells may be bi- or multinuclear and occasionally can transform to tumor giant cells. The number, shape, dimensions and prominent staining of nucleoli is another common feature of malignant neoplastic cells, adding to their anaplasia. Microscopically, many neoplastic cells divide, reflecting their growth activity. In malignant tumors the mitoses are not only abundant but may show either normal or frequently pathological forms (tripolar, or other bizarre shapes). Mitosis counting, DNA measurements, and other techniques can estimate the rate of cellular proliferation. The growth rate of a tumor is a balance between cellular proliferation and cell 57 loss due to ischemic necrosis and apoptosis. The stroma (from the Greek word meaning a mattress) mechanically supports and provides nutrition and metabolic pathways to the neoplastic parenchymal cells. It contains collagen and several other types of fibrils and blood and lymphatic vessels, which grow under the influence of different growth and angiogenic factors. The presence of extensive stromal formation in tumors is called ”desmoplastic reaction”. Stromal myofibroblasts with their contractility are responsible for the puckering and retraction of adjacent structures. Individually dense infiltrates of the stroma composed of lymphocytes, plasmocytes, polymorphonuclear leucocytes, eosinophils and monocytes (macrophages) reflect a host immunopathologic reaction to the antigens presented by tumor cells. 40. FIBROMA Fibroma is a benign, occasionally pedunculated and well-circumscribed tumor arising from ubiquitous fibroblasts occurring in the skin and mucous membranes. Despite the widespread distribution of connective tissue throughout the body, fibromas are surprisingly limited in their sites of origin. Some of the so-called ”fibromas” are more precisely classified as fibromatoses, growing in different anatomical locations, fibroepithelial polyps, irritation fibromas or fibrous hyperplasia (frequently in oral mucosa), hyperplastic fibrous tissue and reno-medullary interstitial cell tumor (a small nodule growing within the renal medulla). This tumor is rich in fully matured and typical fibroblasts and scant or abundant collagenous fibrous connective tissue. The amount of collagen has important influence upon the tumor consistency. The cells may be laid down in random array or sometimes are aligned parallel in broad ribbons. Fibroblastic nuclei tend to be spindle or boat shaped. Delicate intercellular reticulin network may be demonstrated by silver impregnation. 41. FIBROSARCOMA Fibrosarcoma is a spindle cell and collagen and reticulin forming malignant tumor with characteristic histologic appearance. It arises from fibroblasts anywhere in the body, but is most common in the retroperitoneum, in the thigh, in the bones and in the breast. The tumor has locally invasive growth and recurrences are found in over half of the cases. The tumor is capable of early or late metastases, chiefly via the blood stream. Microscopically, the tumor contains all degrees of cell differentiation and is richly cellular. The elongated, predominantly spindle-shaped cells with hyperchromatic polymorphic nuclei lie parallel in interlacing fascicles and contain constantly enlarged nucleoli and plentiful mitoses. Primitive collagen and reticulin fibres are present between the tumor cells. Infiltrative neoplastic growth into the surrounding normal tissues may be observed at the periphery of the tumor. 42. LIPOMA Lipoma is a benign, lobulated and mostly encapsulated tumor derived from mature fat cells. Lipomas are most frequently found in subcutaneous or retroperitoneal adipose tissue or in various organs (e.g. in the bowel wall). Some of the collections of fatty tissue represent the co-called non-neoplastic lipomatous masses, which are developmental in origin and not true neoplasms. Special forms of lipoma are: intramuscular lipoma (so-called infiltrating lipoma), fibrolipoma with admixed fibrous tissue, hibernoma found usually in the shoulder and neck region, angiomyolipoma mostly of the kidney, myelolipoma of the adrenals, retroperitoneum or pelvis, lipoblastomatosis (foetal lipoma) and diffuse lipomatosis on extremities or within the trunk. The tumor is composed of cells that deviate from mature fat cells only in their variation in cell size. The cell borders are distinct. Typically, the rounded nuclei are situated at the cell periphery. The optically empty (clear) cytoplasm appears so because of dissolution of lipids in organic solvents during processing (ethyl alcohol, xylol, benzol). 43. CHONDROMA 59 Chondroma is a benign tumor composed of mature hyaline cartilage. It arises most often centrally within the medullary cavity of(hands and feet short bones. Because of this tendency, it is usually called ”enchondroma”. Osteochondroma is synonymously described as exostosis and represents a developmental aberration rather than true neoplasm. Enchondromatosis (Ollier's disease) is the counterpart of multiple exostoses. In this form there is a considerable risk of transformation in chondrosarcoma. The chondroma found in the lung is a hamartoma and not a true neoplasm. The tumor is composed of lobulated masses of differentiated, i.e. mature hyaline cartilage, separated and encapsulated by a thin layer of connected tissue containing nutritive blood vessels. Cartilage cells are irregularly dispersed throughout the matrix and are located singly or in small groups within clearly defined lacunar spaces. Often there are foci of calcification or/and ossification. 44. OSTEOMA Osteoma regardless of its microscopical structure is a benign lesion consisting of welldifferentiated mature bone tissue, with a predominantly lamellar structure, and showing very slow progression. Osteomas are almost entirely restricted to the skull and mandible and sometimes grow into and diminish paranasal sinuses as dense ivory-like sessile bony masses. If the tumor is composed predominantly of dense, irregularly laid down lamellar bone, it is called eburneating osteoma. If cancellous bone predominates, it is a cancellous osteoma. The Haversian canals in the tumor are narrow and have a smooth lining. The intertrabecular spaces are filled with fibrous stroma that is sometimes highly vascularized and may contain foci of haematopoiesis. 45. CHONDROSARCOMA Chondrosarcoma is a malignant tumor of cartilage. In contrast to osteosarcoma, it grows slowly and metastasizes late not only to long bones but also to the pelvis, ribs, spine and other locations, e.g. in the larynx. Chondrosarcomas vary widely in their clinical behaviour depending on the individual level of anaplasia. Most have a slow clinical evolution and metastasize late, providing a much better prognosis than the more aggressive osteosarcomas. It can develop directly in orthotopic cartilage (so-called primary chondrosarcoma) or in a benign tumor of cartilage (so-called secondary chondrosarcoma). The abnormal cartilage forming tumor mass is much more cellular than the normal cartilage. The neoplastic cells vary in size and some have abnormally large hyperchromatic nuclei with coarse chromatin. Abnormal mitoses are found infrequently. The cartilage cells are irregularly distributed. Multinucleated and giant cells including bizarre forms are frequent. The matrix may show areas of calcification or ossification. The different microscopic features of chondrosarcomas are basis for their histological grading. 46. CAVERNOUS HAEMANGIOMA Cavernous haemangioma is a benign lesion composed predominantly of cavernous vascular structures. The tumor develops most frequently in infancy and childhood in the liver, deep dermis, subcutaneous tissue, lips or in the tongue. The cavernous spaces are filled with fluid blood or sometimes with blood with disturbed flow characteristics that, in rare cases, consumption coagulopathy can occur. A frequent finding in older lesions is an focal organized thrombosis. This tumor in some individuals may be multiple. The neoplastic cavernous (large) vascular spaces are lined by a single layer of endothelial cells and tightly packed with blood cells. Cavernous haemangioma is traversed by connective tissue septa. The tumor mass is sharply defined, but not encapsulated. 47. LEIOMYOMA Leiomyoma is a benign and occasionally richly vascular tumor of smooth muscle cells arising also from blood vessel walls, showing little variation in their appearance and characterized by the presence of non-striated myofibrils within their cytoplasm. Collagen formation present in all leiomyomas may be excessive and at times may obscure the basic structure of the tumor. The tumor occurs less frequently in the superficial skin andalso in deep locations (myometrium /in this location it is frequently multiple – so-called leiomyomatosis/, retroperitoneum, wall of the gastrointestinal tract, breast, bladder, etc.). 61 Histologically it is composed of interlacing smooth muscle cells with elongated, cylindrical, blunt-ended nuclei. Interspersed between groups of neoplastic cells is a dense collagen network. Hyalinization, calcification, and ossification are frequent regressive changes in advanced large tumors. Focal necroses and successive pseudocystic changes are another frequent findings. Mitotic figures are scarce, and giant cells and anaplasia are not present. 48. MALIGNANT FIBROUS HISTIOCYTOMA (MFH) Malignant fibrous histiocytomas are distinctive neoplasms because they are composed of a mixture of cells resembling fibroblasts, myofibroblasts, histiocytes, and primitive mesenchymal cells and cells having intermediate or mixed features (i.e. fibrohistiocytoid cells). Additional features include rich vascularisation and varying numbers of giant cells and lipid-laden xanthomatous cells. It occurs preponderantly in soft tissues, but also occasionally in bone. These neoplasms represent 20 to 30% of soft tissue sarcomas. They may appear at any age with a peak incidence of the more common variant in the seventh decade, somewhat more commonly in males. The sites of origin of soft tissue MFH are lower extremities (approximately 50%), upper extremities (20%), abdominal cavity, retroperitoneum (20%), and other sites uncommonly. Soft tissue lesions grossly are multilobulated, grey-white, fleshy, infiltrative, unencapsulated, but deceptively circumscribed masses. Haemorrhages and areas of necrosis are common. Five histologic variants of MFH have been described. The most common is called storiform-pleomorphic and the next most common is myxoid MFH. The three less common variants are giant cell, inflammatory and angiomatoid variants. The storiform-pleomorphic variant is composed mainly of (1) polygonal histiocytoid cells with prominent oval nuclei, (2) spindle-shaped fibroblasts and myofibroblasts and (3) smallersized non-specialized polygonal to oval mesenchymal cells with small nuclei. Characteristic is the tendency for the spindle cells to be disposed in a cartwheel (storiform) pattern often about slit-like vessels. Pleomorphism, mitotic activity and hyperchromatic tumor giant cells as well as numerous slit-like vessels and scattered lymphocytes or plasma cells are present. Areas of loose myxoid stroma interspersed with areas of cellularity mark the myxoid variant of MFH. The myxoid areas are rich in acid mucopolysaccharides and contain disperse spindled or sometimes stellate mesenchymal cells, some having coarse cytoplasmic vacuoles of mucopolysaccharides. Metastases are present in almost 50% of storiform-pleomorphic lesion at the time of diagnosis, but in only 25% of myxoid tumors. Overall, the five-year survival is approximately 50%. 49. SQUAMOUS CELL PAPILLOMA OF THE ORAL CAVITY This common benign tumor of the oral mucosa occurs on the cheek, gingiva, palate, lips, and tongue. It is found in all ages, even in the childhood, and is usually a solitary lesion. Papillomas vary in size and may be either sessile or pedunculated. Inverted forms are sometimes found. Papillomas present as warty or cauliflower-like growths with white or pink surface depending on the amount of keratin present. Such tumors are likely to share a common pathogenesis with other squamous papillomas in that they result from human papilloma virus (HPV) infection. Histologically they are made up of numerous slender papillae having fibrovascular cores covered by keratinized, stratified squamous epithelium. The arrangement of cells is regular and, as a rule, there is no increase in mitoses nor there are signs of infiltrative growth. Dysplastic changes are rare and malignant transformation is even rarer. 50. PAPILLARY CARCINOMA OF THE THYROID GLAND Papillary carcinoma of the thyroid is the most common form of thyroid cancer. It is one of the malignancies known to be associated with radiation exposure, whether as X-rays to the neck or due to the nuclear fall-out, containing radioactive radioisotopes of iodine, which are selectively trapped by the gland’s epithelial cells. Papillary carcinoma of the thyroid is a slow-growing and well-differentiated form of carcinoma most commonly found in children or in younger adults (less than 45 years old). It presents as non-encapsulated, infiltrative mass, which may be firm and white due to fibrosis. It consists of complicated, ramifying epithelial papillary projections most sharply outlined by the papilliform axial fibrovascular stroma. A single layer of well-oriented, regular 63 cuboidal epithelium covers this framework. In areas the tumor cells may form groups of colloid-containing follicles. All degrees of atypicality and disorientation of cells and formations of glands or sheets of cells may be encountered in the more obviously aggressive lesions. Microscopically, small calcified and layered bluish spherules (the so-called ”psammoma bodies”) are encountered in the axial stroma in almost half of all cases. Some of the epithelial cell nuclei ma reveal central clear areas, representing invaginations of the cytoplasm. For this reason, they are termed ”Orphan Annie eye nuclei”, ”ground glass nuclei” or ”bird’s eye nuclei”. Such nuclei are also used as a criterion for classifying this tumor as papillary. 51. SQUAMOUS CELL CARCINOMA OF THE LIP Cancer of the lip is more common than intra-oral cancers. It is usually seen in elderly people and has a definitive relationship to sunlight exposure. Lip cancers are usually welldifferentiated squamous carcinomas, which spread directly into surrounding tissues, and through the lymphatic vessels to regional lymph nodes. These cancers begin as in-situ lesions, sometimes with surrounding intraepithelial areas of dysplasia. The tumor invades the subepidermal connective tissue as tongues or islands of cancer cells usually surrounded by a prominent inflammatory infiltrate. In well-differentiated tumors, the neoplastic epithelium is obviously squamous in type and consists of prickle cells with a limiting layer of basal cells around the periphery. Intercellular prickles and keratin pearls are often found. In less well-differentiated tumors the keratin pearls are sparse or absent and the prickle cells and their nuclei are much more pleomorphic. In the poorly differentiated forms of these tumors the epithelial cells are even more irregular and primitive so that they may hardly be recognized as squamous cells. 52. BASAL CELL CARCINOMA OF THE SKIN (Basalioma) Basal cell carcinoma is a frequent, locally destructive, slowly expanding skin tumor composed of basal cells. It appears often as ulcerated, irregular lesion with a raised pearly border (so-called ”ulcus rodens”). Basalioma is most common on the face of elderly people. It very rarely metastasizes and is closely associated with chronic sunlight and weather exposure, affecting more lightly pigmented people. As with squamous cell carcinoma, the incidence of basal cell carcinoma raises sharply with immunosuppression and in patients with inherited defects in DNA replication or repair. The indolent clinical behaviour of basal cell carcinoma may relate in part to local immunity limiting the growth of these commonly encountered and usually definitively curable tumors of elderly people. Histologically the tumor is formed by clumps of small dark basophilic cells surrounded by a rim of cells whose nuclei line up like a picket fence (these cells show a typical ”palisade” arrangement reminiscent of the basal layer of the epidermis or follicular epithelium). At least some of the superficially located neoplastic clumps are directly connected with the epidermal epithelium from which the tumor usually originates. Centrally located superficial ulceration is a frequent finding. Two patterns are seen, either multifocal growths originating from the epidermis and extending over several square centimetres or more of skin surface (so-called multifocal superficial type), or nodular lesions, growing downward deeply into the dermis as cords or islands of variably basophilic cells with hyperchromatic nuclei, embedded in a mucinous matrix, and often surrounded by many fibroblasts and lymphocytes. 53. TRANSITIONAL (UROTHELIAL) CELL CARCINOMA OF THE BLADDER Transitional cell or urothelial carcinoma arises from the urothelium and is frequently multiple (multicentric). Carcinoma is often preceded or surrounded by epithelial dysplasia. Painless haematuria is the commonest presenting feature, with dysuria, frequency and urgency occurring in some patients. When found near a ureteric orifice, obstruction causes unilateral pyelonephritis or hydronephrosis. Many of these tumors are papillary, others may be described as flat lesions. Tumor cells are frequently shed into the urine where they can be detected cytologically. Histologically similar tumors arise in the renal pelvises, ureters and in urethra. As shown earlier, most urothelial bladder tumors are papillary, forming delicate fronds 65 covered by an abnormally thick layer of neoplastic urothelium, with atypical cytological features. With increasing cytological abnormalities the likelihood of invasion of the lamina propria increases. Transitional cell carcinomas are graded I – III according to the degree of cytologic atypia exhibited by the cancer cells. This is one guide to prognosis. Staging is also used to judge prognosis (the TNM system is used). A proportion of these tumors may show microscopically foci of squamous, or more rarely, glandular metaplasia. Such tumors are then termed ”mixed tumors”. 54. ADENOCARCINOMA OF THE COLON Cancer of the colon and rectum is one of the commonest forms of malignancy. In the rectum, the majority of cancers are of the ulcerating type, causing bleeding. The annular, stenosing and encircling type is more common in the descending colon and sigmoid, where it usually produces symptoms of obstruction. Polypoid and larger fungous cancers are more common in the right colon where they tend to give rise to recurrent occult bleeding. Ninetyfive percent of all cancers of the colon are adenocarcinomas. In a small proportion of cases adenosquamous carcinomas (in the rectum), small cell undifferentiated carcinomas (of presumable neuroendocrine cell origin) and infiltrative, poorly differentiated carcinomas are occasionally encountered. Unlike the gross pathology, the microscopic characteristics of most right- and left-sided colonic carcinomas are adenocarcinomas, showing varying degrees of mucin production and differentiation of tumor cells. To a limited extent, the degree of differentiation (grade) determines the outlook for the patient after surgery. The grade of differentiation of neoplastic glands varies from place to place even in the same specimen. Much more valuable guide to prognosis is the completeness of excision and the extent of spread. If microscopic examination of the resection margin established that the operation has been potentially curative, then the extent of spread through the bowel wall and the presence of lymph node metastases are the major prognostic determinants. The extent of spread is given by the three Duke’s stages: A. The tumor is confined to the submucosa or muscle layer. B. The tumor has spread through the muscle layer, but does not yet involve the regional lymph nodes. C. Any tumor involving the lymph nodes. 55. NEURINOMA Neurinoma is a round, solitary and discrete tumor, growing intracranially in the pontine-cerebellar angle or extracranially, anywhere in the course of peripheral sensory nerves. These tumors arise from Schwann cells (the synonymous term for this tumor is ”Schwannoma” or ”neurilemmoma”). Histologically, neurinomas exhibit two main patterns: densely packed spindle-shaped cells with frequent nuclear palisading (Antoni A tissue) and more loosely structured areas with myxoid stroma, which may contain small pseudocysts (Antoni B areas). The blood vessels in neurinomas often have hyaline thickening, around which there may be pseudopalisading of tumor cells. By contrast to neurofibromas no nerve fibres are present in the body of the tumor, although the residual nerve of origin of the tumor may be occasionally found compressed to one side. This compression of the nerve of origin of a neurinoma admits the possibility of its complete removal without requiring transection of the nerve. This can be clinically extremely important with acoustic neurinomas: skilled removal of the tumor may help preservation of homolateral auditory function. 56. PIGMENTED NEVUS OF THE SKIN (Nevocellular nevus) Pigmented intradermal nevus represents an advanced or last stage in the evolution of pigmented nevi, in which its evolution is completed. Macroscopically, nevocellular nevi are tan-to-brown, uniformly pigmented, small (usually less than 1 cm), solid regions of elevated skin (papules) with well-defined, rounded borders. In this final stage of development all the junctional melanocytes have entered the dermis. These lesions are often pink because the intradermally located cells produce little or no melanin pigment and because the overlying epidermis contains only normal numbers of active melanocytes. The melanocytes grow in nests only in the uppermost dermis near the dermoepidermal junction (also called ”interface”) and get smaller with depth growing in fascicles or cords and finally individually, being loosely situated between the collagen and elastic fibres. Here the melanocytes frequently become spindle-shaped and even cluster to 67 resemble special neural tissue. This sequence of maturation of melanocytes is of diagnostic importance in distinguishing some benign nevi from malignant melanoma. 57. MALIGNANT MELANOMA OF THE SKIN Malignant melanoma is the malignant variant of pigmented tumors and biologically is characterized by the frequency, with which it metastasizes. Sunlight appears to play an important role in the development of this tumor. Histologically the tumor is composed of melanocytes that resemble in part carcinoma and in part sarcoma cells. These part sarcoma-like and part carcinoma-like cells are absolutely characteristic of malignant melanoma. Cytologic evidences of malignancy are present: cell atypia (cells of different sizes, shapes, nuclear and nucleolar properties), mitoses and invasion of epidermis and dermis. About 10 percent of malignant melanomas are not pigmented (amelanotic melanoma). When present, melanin has a dark brown colour. The melanoma cells grow as poorly formed nests or as individual cells at all levels of epidermis and, in the dermis, as expansible, balloon-like nodules. The growth pattern of the progressed tumor is both horizontal and vertical in individual cases. The nature and extent of the vertical growth phase, however, determines the biologic behaviour of malignant melanoma. Therefore, the depth of vertical invasion of the tumor in the dermis is an important prognostic sign (Clark´s classification). Routinely, for prognostic purposes also the tumor thickness is measured by the method described by Breslow. 58. BENIGN TERATOMA (ADULT CYSTIC TYPE) OF THE OVARY Germ cells differentiate along three embryonic lines from which teratomas may arise. Therefore these tumors contain elements of all three germ cell layers – ectoderm, endoderm and mesoderm, growing usually in younger patients. The possible sites of teratomas are male and female gonads (testis and ovary), retroperitoneum, anterior mediastinum, sacrococcygeal and epipharyngeal regions. The commonest germ cell tumor is ovarian benign cystic teratoma (also called ”dermoid cyst”). It is a dysontogenic neoplasm arising from different embryonic cells and containing among others mostly mature epidermis, skin appendages, and not infrequently, bone or teeth. Macroscopically, the tumor appears as a mass of an irregular mixture of tissues intimately neighbouring with the compressed ovarian tissue and a smoothwalled, unilocal cyst of variable diameter (defined in centimetres), containing sebaceous material and hair. Ten to fifteen percent of these tumors may be bilateral. The cystic space is lined with epidermis-like stratified squamous epithelium, beneath which are found hair shafts, sweat and sebaceous glands, surrounded by tissue equivalent to dermis and subcutaneous fat tissue. Many other tissues may be found admixed in individual biopsy specimens, from other germ layers, such as brain tissue, solid or microcystic structures resembling parts of respiratory, digestive, or endocrine systems. Diagnostically and prognostically most important finding is that all tissues within this tumor are of mature, differentiated character. About 1% of the dermoid cysts may undergo malignant transformation of any one of the component elements (most commonly the squamous cell carcinoma). 59. FIBROADENOMA OF THE BREAST Unlike the situation in other glandular tissues, the commonest type of a benign tumor of the breast is a combined growth of both connective tissue and epithelial (glandular) cells – called fibroadenoma. Benign forms of purely epithelial tumors of the breast (adenomas) also exist but are extraordinary rare. Fibroadenomas occur preferentially in younger women, usually before the age 30. Multiple small areas closely resembling a fibroadenoma are found in some cases of the fibrocystic disease of the breast (in this setting it is called fibroadenomatosis). Fibroadenomas are well-circumscribed, demarcated spherical tumors with a lobulated appearance. Lack of fixation of the tumor to the surrounding and partly compressed breast tissue accounts for its mobility on clinical (manual) examination and easy extirpation at surgery . Their size varies from under 1 cm to more than 10 to 15 cm. The epithelial component of fibroadenoma forms either numerous small, rounded, ductlike structures or thin, branching and curving ductular structures lined by double-layered or flattened breast epithelium, around which are masses of more or less overgrown connective tissue. Small cysts may occasionally be seen. The old morphologic differentiation of fibroadenoma in ”intracanalicular” and ”pericanalicular” subtype is biologically unimportant and therefore abandoned in the recent literature. Such two patterns of epithelial and 69 mesenchymal proliferation often coexist within the same tumor. 60. SEMINOMA OF THE TESTIS Seminoma is the commonest type of testicular malignant tumors, having a germ cell origin, and arising in the seminiferous epithelium from primary germ cells. A homogenous grey-white solid mass, replacing all or part of the body of testis may markedly enlarge the testis harvesting the tumor. Seminomas metastasize preferentially by way of the lymph stream. The commonest, so-called ”typical” or ”classical” subtype of seminoma (85%) is composed of sheets of uniform and pale appearing cells with well-defined cell borders, arranged in islands or lobules. The cytoplasm is vacuolated or watery-appearing and contains glycogen and, rarely, lipid granules. In most of these tumors, the stroma forming delicate septa of fibrous tissue contains a variable lymphocytic infiltrate, a favourable prognostic feature. In some tumors a histiocytic granulomatous response in the stroma along with fibrosis may be found. Mitoses are usually frequent. In 5 to 10% the tumor is anaplastic. The third variant, a spermatocytic seminoma, is encountered in 4 to 6%, affecting older men (over the age of 65) and having excellent prognosis. 61. CHORIOCARCINOMA Choriocarcinoma is a relatively rare, highly malignant neoplasm arising from both trophoblastic layers of human placenta or in germ cell tumors. The tumor cells retain the cytolytic trophoblastic activity giving rise to destructive growth. It grows rapidly and metastasizes early. Most choriocarcinomas arise on the basis of a preexisting hydatidiform mole (about 60 percent of cases). Both the primary tumor and its metastases are unusually haemorrhagic. One of the tumor constituents (syncytiotrophoblast) produces gonadotropin (HCG), and its presence in the blood serves for the diagnosis and estimation of the progression or – if absent – a possible cure of neoplastic disease. HCG can also be easily demonstrated in the choriocarcinoma tissue by means of immunohistochemistry. The tumor is histologically presented by individually large cellular groups of more regular, polygonal Langhans cells (cytotrophoblast) with distinct cell borders as well as by variably formed syncytiotrophoblast in lamellar or vacuolated forms surrounding groups of cytotrophoblastic cells. Among the vital parts, necrotic and haemorrhagic areas are frequently observed and invasion of veins may be also found. Placental villi are never seen within the tumor. 62. INFECTIVE (BACTERIAL) ENDOCARDITIS Infective endocarditis is an acute or subacute inflammation resulting from bacterial infection of a focal area of the endocardium. The line of closure of the heart valves is chiefly involved, but mural endocardium or endocardium of congenital defects (e.g. patent ductus arteriosus or site of the coarctation of the aorta) may be also affected. This disease is frequently observed in unusual hosts such as patients with prosthetic heart valves, the elderly, and drug addicts and gives rise to the state called septicopyemia. The characteristic macroscopic lesion is the vegetation – from small nodules to large or numerous friable, bulky, even several cm long masses adhering to the valve leaflets or to chordae tendineae. At the beginning, deposits of fibrin and platelets adhere to the endocardium. Circulating microorganisms colonise the platelet thrombus and proliferate to form micro-colonies. A thin layer of superficial fibrin prevents the phagocytes from reaching the bacteria. In areas foci of suppuration may be found. Calcification and fibrous thickening of the leaflets indicates that there had been previous inflammation of a different etiopathogenesis with subsequent scarring (e.g. rheumatic endocarditis). A possible finding in examined heart leaflets is destruction, ulceration and perforation of the heart valve and also possible direct spread into the underlying myocardium causing myocarditis . The vegetations in acute endocarditis tend to be bulkier than in the subacute disease. With early diagnosis and appropriate treatment more patients are cured. This is why more and more cases of ”healed endocarditis” are now identified. 63. ACUTE MYOCARDIAL INFARCTION Acute myocardial infarction represents morphologically usually an area of left ventricular necrosis, caused most frequently by ischemia due to coronary artery atheroma 71 with superimposed occlusive thrombus or plaque haemorrhage. Complications include arrhythmias, cardiac failure, mitral incompetence, myocardial rupture leading to haemopericardium, mural thrombosis leading to embolism, and cardiac aneurysm. The chief microscopical feature of an acute, 8 to 12 hours old myocardial infarction is ischemic coagulative necrosis, surrounded by heavy inflammatory cell interstitial infiltration by polymorphonuclear leucocytes at its periphery. The sarcoplasm is homogenized, and the cross-striation is absent. Myocardial nuclei have disappeared, and the necrotic cytoplasm of myofibres is deeply eosinophilic. In the margins of an acute infarction fine droplets of lipids in the viable cells adjacent to those that have died and the so-called ”vacuolar degeneration” or myocytolysis are observed. Another light-microscopical finding in acute phase is edema and haemorrhage. After few days following the acute attack, the first signs of resorption develop and gradual repair by granulation tissue and later fibrosis will be seen during the first weeks following the acute episode. 64. HEALING MYOCARDIAL INFARCTION The necrotic heart muscle will largely be resorbed by macrophages and removed by granulation tissue during the course of 2 – 7 weeks, depending on the size of the infarct. Macroscopically, in the healing phase of fresh myocardial infarction the lesion appears red with remnants of central yellow-brown, usually softened necrotic tissue. Histologically there is an irregularly shaped area with a necrotic zone with disintegration of dead myofibres and resorption of sarcoplasm by macrophages in the centre, a richly cellular layer bordering the necrotic zone, represented by granulation tissue (a fibrovascular response), and bordered in turn by the less deeply eosin-stained normal heart muscle. Now the nuclei of the interstitial tissue cells in the necrotic zone have completely disappeared. Gradually, the granulation tissue replacing the necrotic heart muscle turns into a hypocellular and hypovascular scar. 65. MYOCARDITIS An acute inflammation of the heart muscle has different forms, depending on the histological findings. Serous, purulent, nonpurulent interstitial, granulomatous, giant cell and necrotizing forms create a spectrum of possible morphological findings, depending on the specific causative agent. Macroscopically, the heart during the active phase of myocarditis may appear normal or enlarged with dilatation of all or isolated chambers. The acute inflammatory lesions either resolve, leaving no residue, or undergo progressive fibrosis of different extent, depending on the character and dimension of the original damage to the myocardium. A serous myocarditis is manifested by inflammatory edema of interstitial tissue, separating the individual myofibres. Purulent myocarditis is characterized by metastatic microabscesses in the heart muscle containing bacterial colonies or a phlegmonous neutrophil infiltrate. Nonpurulent interstitial myocarditis has either degenerative character, or lymphohistiocytic form or in some other cases, a granulomatous reaction (e.g. in the active rheumatic fever there are many perivascular Aschoff´s nodules /granulomas/ present). Necrotizing myocarditis is characterized by focal necroses (myocytolysis) of individual amount and lympho-histiocytic infiltrates. Fiedler´s and idiopathic giant cell myocarditis are both characterized by focal necroses associated with a granulomatous reaction containing multinucleate giant cells, interspersed with lymphocytes, many eosinophils, plasma cells and macrophages. 66. ATHEROSCLEROSIS OF THE AORTA Atherosclerosis starts as fatty streaks (lipidosis) early in young individuals. The process of atherosclerosis is initiated by a reaction of smooth muscle cells in the intima and then becomes more progressive and complex. The fundamental lesions of atherosclerosis, the atheromatous plaques, have essentially three components: 1. Cells, including smooth muscle cells, macrophages, and leucocytes; 2. Connective tissue, including collagen, elastic fibres, and proteoglycans; 3. Intra- and extracellular lipid deposits. Typically, the plaques are composed of a superficial part (the fibrous cap), made up of smooth muscle cells with a few leucocytes and relatively dense connective tissue; a cellular area beneath and to the side of the cap, consisting of a mixture of macrophages, smooth muscle cells, and T lymphocytes; and a deeper necrotic ”core”, in which there is a disorganized mass 73 of lipid material, cholesterol clefts, cellular debris, lipid-laden ”foam cells”, fibrin, and other plasma proteins. Particularly at the periphery of the lesions one can see neovascularization of the plaques in older lesions.. Hyalinization and dystrophic calcification is found in individual extent. 67. POLYARTERITIS NODOSA Polyarteritis nodosa is an inflammatory disorder of small and medium-sized muscular arteries of unknown etiology causing among others muscle and joint pain, fever, ischemic lesions in many organs, neuropathy and renal damage. It has been demonstrated recently that many patients have circulating antibody against a cytoplasmic constituent of endothelial cells, associated with alkaline phosphatase. Biopsy of a skin lesion or from other sites may show the histological appearances of necrotizing arteritis. Microscopically, the changes in the vessels may be divided in acute, healing, and healed stages. The acute lesions are characterized by fibrinoid necrosis, which may extent to involve the full thickness of the arterial wall, particularly in small arteries. The necrosis may involve the entire circumference of the wall but it is often localized to a segment. The affected portion may later bulge in an aneurysmal fashion. Healing lesions are characterized by fibroblastic proliferation in addition to the continuing necrotizing process. The adventitial inflammatory infiltrate will now exhibit large numbers of macrophages, eosinophils, and plasma cells. The thrombosis - if present - undergoes organization The healed lesions consist merely of marked fibrotic thickening of the affected arterial wall being sometimes complicated by formation of an aneurysm. The internal elastic lamina and the smooth muscle media are partly or completely destroyed and gradually replaced by fibrous tissue. All three described stages may coexist in the same specimen. 68. ACUTE PURULENT BRONCHITIS Normally, bronchi are sterile, owing to ventilation, phagocytosis, unimpaired immunologic surveillance and mucociliary function. Obstruction of airways, mucociliary insufficiency, retention of mucous secretion, and aspiration may facilitate bronchial infection. Non-specific viral and bacterial inflammation is a frequent form of acute bronchitis. The purulent form of acute bronchitis is recognized by exudate filling the lumen, rich in granulocytes. Other signs of an acute bronchial inflammation are hypersecretion of mucus, hyperaemia, damage and desquamation of ciliary epithelia and leucocytic infiltration of lamina propria mucosae. Similar changes are observed in bronchiolitis. 69. BRONCHIAL ASTHMA Bronchial asthma is defined as increased irritability and responsiveness of the bronchial tree to various stimuli with paroxysmal narrowing of the bronchial airways caused by constriction (bronchospasm), which may reverse spontaneously or after treatment. Microscopically the bronchi are plugged with thick, viscous mucus, containing whorls of shed epithelium, eosinophils, neutrophils, and rarely tiny Charcot-Leyden´s crystals. The latter are collections of crystalloids made up of eosinophil membrane protein. Mucous glands and bronchial wall smooth muscles are hypertrophied. The basal membrane is mostly thickened. Edema, chronic inflammatory cells and eosinophils (5 to 50% of cellular infiltrate) are found in the lamina propria mucosae. 70. BRONCHOPNEUMONIA Pneumonia is usually due to infection affecting distal airways, especially alveoli, with the formation of an inflammatory exudate. The two anatomical patterns, lobar pneumonia and bronchopneumonia, can result from infection by one of several types of bacteria, or other pathogens. Sometimes these two patterns overlap. Bronchopneumonia has a characteristic patchy distribution, centred on inflamed bronchioles and bronchi with subsequent spread to surrounding groups of alveoli. Histology shows focal acute inflammation of the lungs with suppurative exudate filling the bronchi, bronchioli and adjacent alveoli. Besides polymorphonuclear leucocytes, the exudate contains small amount of fibrin, causative microorganisms (better demonstrated by bacterioscopic stains /e.g. Gram stain/), macrophages and desquamated pneumocytes. With 75 antibiotics and physiotherapy, the areas of bronchopneumonia may fully resolve during the course of the disease, or, under bad circumstances, heal by organisation of exudate by granulation tissue and scarring (so-called ”carnification”) within the alveoli and bronchioles. 71. LOBAR PNEUMONIA Lobar pneumonia is an acute bacterial infection of a large portion of a lobe or of an entire lobe of the lung. It tends to occur at any age but is relatively uncommon in infancy and in late life. Classic lobar pneumonia is now encountered much less often, owing to the effectiveness with which antibiotics abort these infections and prevent the development of fullblown lobar consolidation. 90 – 95% of all lobar pneumonias are caused by pneumococci (Streptococcus pneumoniae); occasionally Klebsiella pneumoniae, staphylococci, streptococci, Haemophilus influenzae, and some of the gram-negative organisms, such as the Pseudomonas and Proteus bacilli, are also responsible for this lobar distribution of involvement. The most common portal of entry is the air passages. A lobar distribution appears merely to be a function of the virulence of the organism and the vulnerability of the host. Heavy contamination by virulent pathogens may evoke this pattern in healthy adults, whereas organisms of lower virulence may accomplish the same in the predisposed patient. In lobar pneumonia there is more extensive exudation that leads to spread through the pores of Kohn. Moreover, the copious mucoid encapsulation produced by the pneumococci protects the organisms against immediate phagocytosis, and thus favours their spread. Four stages of the inflammatory response have classically been described: The first stage of congestion represents the developing bacterial infection at lasts for about 24 hours (and thus is rarely seen histologically). It is characterized by vascular engorgement, intra-alveolar fluid with few neutrophils, and often the presence of numerous bacteria. Grossly, the involved lobe is heavy, boggy, red and subcrepitant. The stage of red hepatisation that follows on the second and third days is characterized by increasing numbers of neutrophils and the precipitation of fibrin to fill the alveolar spaces. The massive confluent exudation obscures the pulmonary architecture. Extravasation of red cells causes the coloration seen on gross examination. In many areas, the fibrin strands stream from one alveolus through the pores of Kohn into the adjacent alveolus. The white cells contain engulfed bacteria. An overlying fibrinous or fibrinosuppurative pleuritis is almost invariably present. On gross examination, the lobe now appears distinctly red, firm, and airless with a liver-like consistency, hence the term hepatisation. The stage of grey hepatisation follows from the fourth to sixth day with a continuing accumulation of fibrin associated with the progressive disintegration of inflammatory white cells and red cells. This exudate contracts somewhat to yield a clear zone adjacent to alveolar walls. In the usual case, the alveolar septa are preserved. The progressive disintegration of red cells and the persistence of fibrinosuppurative exudate give the gross appearance of a greyishbrown, dry surface. Sometimes, when the bacterial infection extends into the pleural cavity, the intrapleural fibrinosuppurative reaction produces what is known as empyema. The final stage of resolution (yellow hepatisation) follows in the great preponderance of cases with a favourable outcome on the seventh and eighth days. The consolidated exudate within the alveolar spaces undergoes progressive enzymic digestion to produce granular, semi fluid debris that is resorbed, ingested by macrophages, or coughed up. In such favourable cases, the normal lung parenchyma is restored to its normal state. The pleural reaction may similarly resolve, but more often it undergoes organisation, leaving fibrous thickening or permanent adhesions. Many complications may supervene during this classic evolution. The type 3 pneumococcus and the Klebsiella bacillus characteristically produce an abundant mucinous secretion. These same organisms and the staphylococci frequently cause abscess formation. Organization of the exudate may convert the lung into a solid tissue (the process called carnification). Bacteremic dissemination to the heart valves, pericardium, brain, kidneys, spleen, and joints may cause metastatic abscesses, endocarditis, meningitis, or suppurative arthritis. 72. PRIMARY ATYPICAL PNEUMONIA The term primary atypical pneumonia (PAP) was initially applied to an acute febrile respiratory disease characterized by patchy inflammatory changes in the lung, largely confined to alveolar septa and pulmonary interstitium. The term ”atypical” denotes the lack of alveolar exudate, but a much more accurate designation is interstitial pneumonitis. The pneumonitis is caused by a variety of organisms, the most common being Mycoplasma pneumoniae. Other etiologic agents are viruses, including influenza virus types A and B, the respiratory syncytial viruses (RSV), adenovirus, rhinoviruses, and rubella and varicella 77 viruses; Chlamydia (psittacosis); and Coxiella burnetii (Q fever). In some cases, the cause is undetermined. Any one of these agents may cause merely an upper respiratory tract infection, recognized as the common cold, or a more severe lower respiratory tract infection. The circumstances that favour such extension of the infection are often mysterious but include malnutrition, alcoholism, and underlying debilitating illnesses. All causal agents produce essentially similar morphologic patterns. The pneumonic involvement may be patchy or may involve whole lobes bilaterally or unilaterally. The affected areas are red-blue, congested, and subcrepitant. Predominant in histologic pattern is the interstitial nature of the inflammatory reaction, virtually localized within the wall of alveoli. The alveolar septa are widened and oedematous and usually have a mononuclear inflammatory infiltrate of lymphocytes, histiocytes, and occasionally plasma cells. In very acute cases, neutrophils may also be present. The alveoli may be free of exudate, but in many patients there are intra-alveolar proteinaceous material, a cellular exudate, and characteristically pink hyaline membranes lining the alveolar walls, similar to those seen in hyaline membrane disease of infants. These changes reflect alveolar damage similar to that seen diffusely in the adult respiratory distress syndrome. Subsidence of the disease is followed by reconstitution of the native architecture. 73. FIBROPLASTIC PLEURITIS (Pleurisy) Pleuritis may result from the extension of any pulmonary infection to the visceral pleura, bacterial infections within the pleural cavity, viral infections, or pulmonary infarction that involves the surface of the lung. The most striking symptom is sharp, stabbing chest pain on inspiration. In acute inflammatory conditions of the lung such as lobar pneumonia, an inflammatory exudate may form in the pleural cavity, with deposition of fibrin on the visceral pleura. After the acute phase of the illness, fibrin on the pleural surface undergoes organization. All the fibrin has not been removed by the macrophages and the fibroblasts in the granulation tissue have formed considerable amounts of collagen, thereby converting the granulation tissue into cellular but still fairly vascular fibrous tissue. The end-result will be a layer of fibrous tissue, which if abundant may greatly restrict the respiratory movements of the lung. If this thickened pleura is peeled off, pulmonary function improves markedly. It is likely that the process designated “shrinking pleuritis with atelectasis”, “folded lung syndrome”, or “round atelectasis” represents a variation on this theme. 74. SQUAMOUS CELL CARCINOMA OF THE LUNG Squamous cell carcinoma is probably the most common type of bronchogenic carcinoma. Squamous carcinomas are more common in men than in women, usually develop in middle or later life, and are strongly associated with cigarette smoking. Roughly two thirds of squamous carcinomas are central tumours, involving the main or lobar bronchi, whereas one third arise in the lung periphery, either in small bronchi or in association with scars. Bronchial involvement may take the form of a warty endobronchial protrusion, or the tumour may ulcerate the bronchus and grow outward. If the tumour obstructs a large bronchus, the lung distal to the tumour will often be the site of obstructive pneumonia and bronchiectasis. The most common symptoms, in decreasing order of frequency, are cough, weight loss, pain, increased sputum production, haemoptysis, malaise, fever, and those resulting from paraneoplastic manifestations. Peripherally located lesions are clinically silent until they reach a sufficient size to ulcerate into a bronchus or to involve the pleural space. Carcinomas located in the superior pulmonary sulcus result in a clinical picture peculiar to their location, known as Pancoast's syndrome. This is characterized by pain in the distribution of the ulnar nerve and is often accompanied by Horner's syndrome secondary to involvement of the sympathetic chain. Microscopically, the diagnosis of malignancy is based on cell atypia and invasiveness, and the diagnosis of squamous cell type on the detection of keratin and/or intercellular bridges. Keratinised cells can be recognized in sections by their brightly eosinophilic refractile and pyknotic nuclei. Whorls or eddies of cells may be keratinised (epidermoid pearls), the whole centre of the lobule may be filled with keratin, or at the other extreme only a few single cells may be keratinised. 75. SMALL CELL CARCINOMA OF THE LUNG Small cell carcinoma comprises 10% to 20% of all lung cancers. Most of the patients are males, their median age is 60 years, and 85% or more are smokers. Small cell carcinoma 79 is typically a lesion of the central portions of the lung, but occasionally it is found in a peripheral location. Grossly, the tumour is white-tan, soft, friable, and extensively necrotic. When centred in a large bronchus (the usual situation), it may involve it in a circumferential fashion and/or spread widely beneath the normal mucosa. The bronchus may be totally occluded in the late stages, but pure or predominant endobronchial involvement is highly unusual. Microscopically several patterns are recognized. The oat cell type consists of round or elongated poorly cohesive cells 10 to 12 m in length or slightly larger than lymphocytes. The tumour cells have dark clumped cytoplasm. The nuclei are finely granular and very hyperchromatic, nucleoli are inconspicuous, mitoses are frequent, and the cytoplasm is so scanty as to be unrecognisable in routine preparations. In some instances the cells have an elongated (fusiform) shape. Nuclear "molding," a change first described in cytologic smears, can also be appreciated in microscopic preparations. Necrosis is usually present and widespread in larger tumours. The pattern of tumour growth is diffuse but with some division into lobules by vessels and stroma, which helps to distinguish oat cell carcinoma from lymphoma. Small cell carcinoma is highly malignant and almost invariably has metastasised by the time of diagnosis. 76. EXTRAMEDULLARY HAEMATOPOIESIS Extramedullary haematopoiesis is characteristic for a number of blood diseases, including pernicious anaemia, the haemolytic anaemias and the leukaemias. It also occurs with extensive metastases to bone. Also it may be presented in immature newborn liver. Histologically, there are numerous focal infiltrates that under higher magnification are revealed as groups of cells in dilated sinuses making the pressure atrophy of surrounding parenchyma. The cells here are primarily of the erythropoietic sequence (particularly erythroblasts and normoblasts), large cells with pale nuclei and light basophilic cytoplasm or smaller cells with pyknotic nucleus and a thin rim of pink coloured cytoplasm. But there are also cells from the leucocytic series, from which eosinophilic myelocytes and mature leukocytes predominate, and even some megakaryocytes. In Kupffer cells, less in hepatocytes, iron pigment in different amount is present. In portobiliar spaces also rich haematopoiesis happens with the infiltration of the connective tissue stroma with erythropoietic and leukopoietic cells. In long lasting process connective tissue diffusely enhances, which tends to the liver fibrosis. 77. CHRONIC LYMPHOCYTIC LEUKAEMIA (CLL) IN THE LIVER Chronic lymphocytic leukaemia (CLL) is the most common leukaemia in the elderly, with 90% of cases occurring after 50 years of age. CLL is the most indolent of all leukaemias. Males are affected twice as commonly as females. Patients with more advanced disease and correspondingly poorer prognosis exhibit mild but generalized lymphadenopathy, hepatoand splenomegaly, anaemia and thrombocytopenia. CLL shows considerable overlap with small lymphocytic lymphoma. The vast majority of cases are of B-cell type. T-cell CLL is rare, less then 5% of all cases. Patients with CLL are often asymptomatic. When the symptoms are present, they are non-specific and include easy fatigability, loss of weight, and anorexia. Total leukocyte count may be increased only slightly or may reach 200000 per mm3. In all cases there is absolute lymphocytosis of small, mature-looking lymphocytes. Only a small fraction of lymphocytes are large ones with indented nuclei and nucleoli. Smudge cells (crushed nuclei of lymphocytes) are commonly seen in peripheral smears. Because the leukaemic B-cells are non-functional, these patients often have hypogamaglobulinaemia and increased susceptibility to bacterial infections. The course and prognosis of CLL are extremely variable and depend primarily on the clinical stage. Overall, the median survival is four to six years. Transformation to acute leukaemia with blast crisis is rare. Microscopically in chronic lymphatic leukaemias the immature cells (lymphoblasts, lymphocytes) permeate the periportal fields, while the sinusoids contain only a limited number of nucleated cells. Under low magnification, the significantly dilated, bluish periportal fields are prominent. They are usually spherical. Median and high magnifications reveal infiltration of the periportal connective tissue by lymphatic cells having dense and vesicular nuclei with little cytoplasm. Macroscopically organ is enlarged. 78. CHRONIC MYELOID LEUKAEMIA (CML) IN THE LIVER Chronic myelocytic leukaemia (CML), one of the myeloproliferative disorders, is a neoplasm derived from pluripotential stem cell, in which differentiated cells of the 81 granulocytic series predominate in the blood and marrow. CML occurs in all ages and both sexes but predominantly in middle-aged adults. A slight male preponderance has been noted, but the clinical course of the disease is similar in both sexes. CML is associated with the presence of a distinctive chromosomal abnormality, the Ph1 (Philadelphia) chromosome. The onset of CML is usually slow, and the initial symptoms may be quite non-specific. They are caused by anaemia or by hypermetabolism due to increased cell turnover and include easy fatigability, weakness, weight loss, and anorexia. Sometimes the first symptom is a dragging sensation in the abdomen caused by the extreme splenomegaly characteristic of this condition. Usually, there is marked elevation of the leukocyte count, commonly exceeding 100000 cell per mm3. The course of CML is one of slow progression, and even without treatment a median survival of three years can be expected. After a variable period averaging three years, approximately 50% of patients enter an ”accelerated phase”, during which there is a gradual failure of response to treatment, increasing anaemia and thrombocytopaenia, acquisition of additional cytogenic abnormalities, and finally, transformation into a picture resembling acute leukaemia (”blast crisis”). In the remaining 50%, blast crisis occur abruptly without an intermediate accelerated phase. Morphologically, the myeloid cells appear relatively normal. However, leukaemic neutrophils failing to differentiate normally are indicated by low or absent leukocyte alkaline phosphatase and inadequate phagocytic activity. The unrestricted increase in the number of immature, early forms of granulocytes leads to the accumulation and multiplication of myeloblasts, promyelocytes and myelocytes in the sinusoids of the liver. Under low magnification the organ structure appears to be intact. Under median magnification there is a marked increase in the cellular content of the sinusoids. The sinusoids are dilated and tightly packed with large nucleated cells. The periportal fields are infiltrated only slightly or not at all. The liver cells may show evidence of pressure atrophy and degenerative changes. 79. NON-HODGKIN´S LYMPHOMA (NHL) IN LYMPH NODE Lymphomas other than Hodgkin’s arise from lymphocytes (B cells or T cells) or from histiocytes (histiocytic lymphomas, malignant histiocytomas). The usual presentation of NHL is a localised or generalised lymphadenopathy. In about one third of cases it may be primary in other sites where lymphoid tissue is found, e.g., in the oropharyngeal region, gut, bone marrow, and skin. Lymphomatous involvement often produces marked nodal enlargement, which is almost always nontender. Some, after becoming widespread, spill over into the blood, creating a leukaemia-like picture in the peripheral blood. Although we speak of NHL as a group, we should recognise that it encompasses a wide spectrum of disorders, differing in patient age of onset, the cells of origin, and response to therapy. It is therefore necessary to classify NHL into various subgroups. Well-differentiated lymphocytic lymphoma consists of mature lymphocytes and may be regarded as the counterpart in the tissue of chronic lymphocytic leukaemia. The normal architecture of the node has been replaced by a diffuse infiltrate of small round cells resembling mature lymphocytes. They are fairly uniform in size and shape, with deeply staining nuclei and only a sparse rim of cytoplasm. There is no evidence of follicle formation. Larger pale-staining histiocytes with large vesicular nuclei are scattered amongst them. The vast majority of the cells are small lymphocyte – type cells with round basophilic nuclei and thin rim of cytoplasm. Lymphoblastic lymphoma occurs at all ages but most often in children and adolescent. The normal population of cells of this node has been replaced by a monomorphic infiltrate of cells with ovoid or round nuclei, in which the chromatin is evenly dispersed. Multiple small nucleoli are visible in some nuclei. Cytoplasm is fairly scanty and not well defined. 80. MULTIPLE MYELOMA (Plasmacytoma) Multiple myeloma is basically a multifocal plasma cell cancer of the osseous system that in the course of its dissemination may involve many extraosseous sites. Plasma cell myeloma, or multiple myeloma, is characterized by proliferation and accumulation of neoplastic cells within the marrow that usually constitute greater than 20% of the marrow cells that morphologically resemble plasma cells. Usually the myeloma cells secrete immunoglobulins (Ig), light chains (Bence Jones protein), or both. IgG and IgA are most frequent, IgD and IgE are rarely secreted, and nonsecretory myeloma occurs in 1% of cases. Within the marrow, proliferations may be diffuse or form nodular masses. The diagnosis can usually be made by iliac crest biopsy. Clinical manifestations stem from the effects of 83 infiltration of organs, particularly the bones, by tumourous masses of plasma cells; and the abnormal immunoglobulins secreted by the tumour cells. Microscopically the marrow in myeloma is infiltrated by plasma cells that may exhibit a range of cytologic appearances. Most commonly, the tumour cells closely resemble mature plasma cells, forming extensive perivascular and paratrabecular infiltrates, scattered nodules or confluent infiltrates. But all ranges of immaturity may be encountered, including undifferentiated cells resembling lymphoid precursors as well as lymphocyte-plasma cell intermediates. Important is their abnormal aggregation or evidence of their destructive potential in the form of infiltration, invasion, and erosion. In a section or smear of bone marrow, characteristic atypical plasma cells are present that have eccentric nuclei with chromatin arranged like the spokes of a wheel. There may be multinucleated plasma cells and giant cells. The protein aggregates may appear as acidophilic inclusions known as Russel bodies, but are not pathognomic. The bone resorption results from the activation of osteoclasts by osteoclast-activating factors secreted by the myeloma cells. Grossly, on section the bony defects are filled with red, soft, gelatinous tissue. 81. PLEOMORPHIC ADENOMA OF THE SALIVARY GLAND Pleomorphic adenoma is the most common tumour of the parotid, submandibular, and other minor salivary glands, they constitute 65 – 80% of tumours in the major salivary glands. The palate is the most common site for pleomorphic adenomas arising from the minor salivary glands and occurring on the hard and soft palates with about equal frequency. Because of their remarkable histologic diversity, these neoplasms have in the past been called mixed tumours. They may appear at any age, most frequently in the fifth and sixth decades, with a small but distinct female preponderance. The great majority arise in the parotids and only rarely in the other major and minor salivary glands. Single tumours are the rule, but rarely two or more lesions appear simultaneously on the same or both sides. Grossly the tumours are rounded to bossed, somewhat lobulated masses ranging up to 6 cm in greatest dimension, and surrounded by a fibrous capsule of varying thickness. Expansive growth produces tongue like protrusions that may be left behind at the surgical excision, accounting for the recurrence rate of 5 to 50%. The cut surface is grey-white with variegated myxoid areas and areas of blue translucence representing chondroid. In essence, they are composed of epithelial elements dispersed throughout a matrix of mucoid, myxoid, and chondroid tissue. In some lesions, the epithelial elements predominate, but in others the reverse obtains. The epithelial elements form ducts, acini, irregular tubules, or strands or sheets of cells, or squamous structures. They have ductal or myoepithelial origin. The cells lining ductal or glandular formations are cuboidal or columnar, and often there is PAS-positive secretion within the glandular or ductular spaces. Often small, dark, spindled, myoepithelial cells underlie the cuboidal epithelium to create distinctive double strands of epithelial cells. In addition, the myoepithelial elements may be dispersed in islands or strands, often embedded within a loose connective tissue or myxoid tissue. The myoepithelial cells may be present as eosinophilic spindle cells resembling smooth muscle. Hyaline, myxoid, chondroid or rarely bone areas result from the accumulation of mucoid or hyaline material between myoepithelial cells, which alter their appearance. Accumulation of basophilic mucoid material separates the myoepithelial cells, and vacuolar degeneration of the myoepithelial cells results in an appearance very similar to cartilage. The epithelial and apparent mesenchymal elements are randomly intermixed. The histologic diversity is almost limitless, but it is precisely this feature that characterises the pleomorphic adenoma. 82. OESOPHAGEAL VARICES Portal hypertension, when sufficiently prolonged or severe, induces the formation of collateral bypass channels wherever the portal and caval systems interdigitate. The collaterals here develop in the region of the lower oesophagus when portal flow is diverted through the coronary veins of the stomach into the plexus of oesophageal submucosal veins, thence into the azygous veins, and eventually into the systemic circulation. The increased pressure in the oesophageal plexus produces tortuous vessels called varices. In addition to the most often cause of hepatic cirrhosis, oesophageal varices result from superior vena cava obstruction, portal vein thrombosis, hepatic vein thrombosis (Budd-Chiari syndrome), pylephlebitis, and tumour compression of the major portal trunk. Varices occur in approximately two thirds of all cirrhotic patients and are most often associated with alcoholic cirrhosis. They are less commonly found in association with pigment cirrhosis and postnecrotic scarring of the liver and are rarely produced by biliary or cardiac cirrhosis. Very infrequently, varices are encountered in systemic amyloidosis and sarcoidosis. 85 Furthermore, rare cases have been described without evident cause for the portal hypertension. Rupture and bleeding are the most serious problems related to oesophageal varices. Varices appear as tortuous dilated veins lying primarily within the submucosa of the distal esophagus and proximal stomach; venous channels directly beneath the esophageal epithelium may also become massively dilated. The net effect is irregular protrusion of the overlying mucosa into the lumen. When the varix is unruptured, the overlying mucosa may be normal, but often is eroded and inflamed because of its exposed position. If rupture has occurred in the past, thrombosis or superimposed inflammation may be seen. They are covered by a thin mucous membrane. The increased venous pressure, with or without inflammation or ulceration, often results in massive and frequently fatal haemorrhage. 83. CHRONIC PEPTIC ULCER OF THE STOMACH Ulcers are defined as a breach in the mucosa of the alimentary tract, which extends through the muscularis mucosa into the submucosa or deeper. Peptic ulcers are chronic, most often solitary, lesions that occur in any portion of the gastrointestinal tract exposed to the aggressive action of acid-peptic juices. Both the acid and the pepsin are critical. They tend to be less than 4 cm in diameter, may penetrate muscularis mucosa or perforate gastric wall. They are frequently recurrent, with intermittent healing and are located in the following sites with decreasing frequency: duodenum, first portion; stomach, usually antrum; within Barrett´s mucosa; in the margins of a gastroenterostomy (stomal ulcer); in the duodenum, stomach, or jejunum of patients with Zollinger-Ellison syndrome; within or adjacent to a Meckel´s diverticulum that contains ectopic gastric mucosa. Chronic ulcers occur with a frequency of 2,5% and 1,4% respectively, among men and women. Gastric ulcers are more frequent at an older age, with preponderance among blood groups A. The typical peptic ulcer is small (about 1 to 2,5 cm in the stomach). Microscopically four zones are demonstrable: (1) The base and margins have a superficial thin layer of necrotic fibrinoid debris and beneath this layer the zone of nonspecific inflammatory infiltrate, with polymorphonuclear leucocytes predominating; (2) it is lying on an intensely eosinophilic layer of fibrinoid necrosis; (3) that is bordered by granulation tissue infiltrated with mononuclear leucocytes in the deeper layers, especially in the base of the ulcer; and (4)the granulation tissue rests on a more solid fibrous or collagenous scar. Vessel walls within the scarred area are typically thickened by the surrounding inflammation and are occasionally thrombosed. 84. CHRONIC GASTRITIS Chronic gastritis is defined as the presence of chronic mucosal inflammatory changes leading eventually to mucosal atrophy and epithelial metaplasia, usually in the absence of erosions. The epithelial changes may become dysplastic, and constitute a backround for the development of carcinoma. Chronic gastritis is notable for distict causal subgroups, location of disease in the stomach (e.g. antral, corporal), histology, and clinical features. Patterns of gastritis also vary in different parts of the world. The major etiologic associations of chronic gastritis are as follows: Immunologic, associated with pernicious anemia; Chronic infection, especially Helicobacter pylori; Toxic, as with alcohol consumption and cigarette smoking; Postsurgical, especially following antrectomy and gastroenterostomy with reflux of bilious duodenal secretions; Motor and mechanical, including obstruction, bezoars (luminal concretions), and gastric atony; Radiation; Granulomatous conditions (e.g. Crohn´s disease); Miscellaneous – graft versus host disease, amyloidosis, uremia. So-called atrophic gastritis is not properly classified as an inflammatory condition. Some uses the term as a synonym for gastric atrophy. It may affect different regions of the stomach and exhibit varying degrees of mucosal damage. Regardless of cause or location, the morfologic features are similar. By visual inspection, the mucosa is usually reddened and has a coarser texture than normal. There may be some flattening of the mucosa. With more severe chronic gastritis, the mucosa becomes more obviously thinned and flattened. By microscopy, an inflammatory infiltrate of lymphocytes and plasma cells is present within the lamina propria. In the early stages, this infiltrate is usually limited to the upper third of the gastric mucosa (chronic superficial gastritis). In more severe forms, the 87 inflammatory infiltrate involves the full thickness of the mucosa. Lymphoid aggregates, some with germinal centers, are frequently observed in the mucosa. The response of the epithelium to injury is increased mitotic activity in the neck region of the gastric glands. The less mature cells that populate the mucosa exhibit enlarged, hyperchromatic nuclei, and diminished to absent mucin vacuoles. Metaplastic columnar absorptive cells and mucous goblet cells of intestinal phenotype (primarily small intestine) may partially replace portions of the gastric mucosa. The body-fundic mucosa also may exhibit the simpler glands characteristic of the antral-pyloric region. Atrophic change is evident by marked loss in glandular structures corresponding to the mucosal flattening observed grossly. 85. TRANSMURAL INFARCTION OF SMALL BOWEL (Infarsatio haemorrhagica intestini tenuis) Infarction of the small bowel can result from either venous or arterial obstruction. The infarction, however, is always haemorrhagic, and extensive haemorrhage has occurred into the mucosa and the deeper tissue. The muscularis mucosae appears viable, with well-stained nuclei. The villi, however, have lost their epithelial covering and have collapsed. The small blood vessels are greatly dilated. The crypts of the glands retain their epithelial cells, although they appear somewhat degenerated. Thrombosis of the mesenteric veins, this cause of intestinal ischemic occurs under a variety of conditions. Almost all thromboses affect the superior mesenteric veins, whereas only 5% of the cases involve the inferior mesenteric veins. The collateral flow in the distribution of the superior mesenteric vein is usually sufficient to preclude infarction of the intestine. However, the thrombosis of smaller veins can also lead to transmural infarction. The infarcted bowel is edematous and diffusely purple. The demarcation between infarcted bowel and normal tissue is usually sharp, although venous occlusion may lend to a more diffuse appearance. Extensive haemorrhage is seen in the mucosa and submucosa, the former becoming necrotic. Although the deep muscle layers are initially preserved, they eventually also become necrotic. The mucosal surface shows irregular white sloughs, the wall becomes thin and distended, and bubbles of gas may be present in the mesenteric veins. 86. CARCINOMA OF THE STOMACH The incidence of carcinoma of the stomach varies greatly in various parts of the world and among various people. It is known to be particularly frequent in Japan. Most carcinomas of the stomach arise from the mucus secreting cells. Differentiation is variable as to the extent and regularity of gland formation, mucus secretion, cytologic features, etc., but in general they tend to be less well-differentiated and less characteristic than the carcinomas of the colon and rectum. Early cancer of stomach is an epithelial infiltrating tumor that is limited to the mucous membrane. It frequently shows a structure similar to that of the signet-ring carcinoma. The mucous membrane is still maintaned so that infiltration is freqeuntly missed. The stroma includes small groups of pale cells that can be identified as signet-ring cells under higher magnification and particularly with PAS stain. Mucinous carcinoma. This condition is characterized morphologically by extreme mucin production. The large, lightly basophilic, finely stranded mucous masses can easily be taken for edema of the stroma. They enclose small groups of cancer cells that demonstrate only occasional intracytoplasmic mucous degeneration, much like the signet-ring carcinoma. Scirrhous carcinoma. The scirrhous carcinoma has particularly fiber-rich stroma that includes only scattered, individual cancer cells. Low magnification shows the marked thickening of the gastric wall. Under higher magnification, the small groups of carcinoma cells can be seen. They have large nuclei and particularly prominent nucleoli. The Van Gieson-red collagen fibres and fibroblasts enclose them. Very fiber-rich scirrhous carcinomas may present a difficult problem. 87. SUBACUTE HEPATIC NECROSIS Frequently a more serious variant of acute viral hepatitis is that described by some investigators as progressive viral hepatitis, which eventually may be fatal. Frequently, the histologic changes in the liver resemble those of the usual form of acute viral hepatitis. However, in addition, multiple, larger zones of liver cell necrosis may be seen, which are confluent, resulting in bridging bands of collapsed stroma infiltrated by lymphocytes that connect adjacent portal areas or central regions. Such bridging lesions have been called subacute hepatic necrosis, and their presence 89 indicates a severe form of the disease that progress to hepatic failure and death or to cirrhosis. Subacute hepatic necrosis sometimes may be difficult to distinguish from the lesion of chronic active hepatitis. 88. MICRONODULAR HEPATIC CIRRHOSIS The currently accepted definition of cirrhosis requires the term be applied to a liver with diffuse fibrosis and containing regenerative nodules, which are masses of hepatocytes lacking the normal blood flow because of the lack of terminal hepatic venules. Micronodular cirrhosis applies to the liver, in which nearly all the nodules are less than 3 mm in diameter though some have used 1,5 mm as the maximum diameter because that is the diameter of a normal lobule. Examples of common micronodular cirrhosis include alcoholic cirrhosis, biliary tract obstruction, and hepatic venous obstruction. Micronodular cirrhosis develops from a chronic inflammation in the periportal area with secondary periportal necrosis. This frequently results in the appearance of large and regular parenchymal islands of similar size surrounded by a ring of connective tissue. The central vein may be in the centre or in the periphery of the parenchymal islands. 89. HEPATOCELLULAR CARCINOMA IN CIRRHOSIS This is a malignant tumor that originates from the hepatocytes. Malignant hepatomas develop most frequently in liver that has undergone cirrhotic changes. The well-known hepatic carcinogens include arsenic, thorotrast, PVC, and others. Histologically, the carcinoma consists of solid, trabecular or alveolar cell clusters. The tumor cells still resemble hepatocytes, but more frequently they have a dark nucleus and show mitoses and cellular atypia. The infiltrating growth and the invasion of blood vessels is characteristic of this tumor, which can also produce an amorphous, yellowish-brown bile pigment. 90. CHRONIC CHOLECYSTITIS As a rule, cholecystitis is a chronic, recurent, nonbacterial inflammation of the gall bladder. In chronic inflammation the wall is thickened (chronic hyperplastic cholecystitis). Chronic cholecystitis is more common in elderly adipose women and is accompanied by cholelithiasis in more than 90% of all cases. In the acute stage cholecystitis is usually nonbacterial and is caused by a perfusion disturbance. The mucosal folds are widened by lymphocytic infiltration and fibrotic connective tissue proliferation. The surface epithelium undergoes glandular transformation and resembles Brunner´s glands (intestinal metaplasia). The increased pressure in the lumen leads to diverticulum like outpouchings of the mucous membranes (Rokitansky-Aschoff´s sinus). These are empty spaces, lined with cylindrical epithelium that extends beyond the muscularis. In an advanced stage of chronic cholecystitis, scarring and flattening of the mucosal folds predominate (chronic atrophic cholecystitis). In the terminal stages of this inflammatory process the wall of the gall bladder consists of scar tissue only. This is known as porcelain gall bladder. 91. ACUTE HAEMORRHAGIC PANCREATITIS Parenchymal and fat tissue necrosis of the pancreas is considered to be autodigestive in nature (trypsin, lipase) and follows a local circulatory disturbance. The pathogenesis of this highly complex process is still a matter of debate. Macroscopically in the initial stages there is edema and focal parenchymal necrosis (large, dirty gray pancreas). In haemorrhagic necrosis the pancreas is dark red and haemorrhagic. Secondary liquefaction and cavitation are late developments. Adipose tissue necrosis appears as white, scattered foci. The condition is most frequent in obese women and in patients with alcoholic fatty degeneration of the liver. Very early in the disease the pancreas microscopically shows only interstitial edema. Later the pancreas contains patches of coagulative necrosis rimmed by infiltrates of polymorphonuclear leukocytes. Still later, necrosis of arteries and arterioles is responsible for gross haemorrhages. Veins often are thrombosed. Eventually, as bacteria lodges in the necrotic pancreas, through either the ducts or bloodstream, frank suppuration may occur. A late complication of acute pancreatitis is the occasional development of a pseudocyst – an accumulation of enzyme-rich fluid, necrotic debris, and altered blood confined not by an 91 epithelial capsule, but by retroperitoneal connective tissue, adherent upper abdominal viscera, and the peritoneal components of the lesser omental sac. 92. POLYCYSTIC KIDNEY DISEASE Polycystic kidney disease or autosomal dominant polycystic renal disease is more common than autosomal recessive (infantile) polycystic renal disease. The disease is inherited as an autosomal dominant disorder with high penetrance associated with locus on autosome 16. Grossly the kidneys are often huge, weighing more than 150 g apiece. The innumerable cysts, varying from barely visible to 5 cm in size, produce a cobblestone-like external surface. On cross section the cysts contain straw yellow, haemorrhagic, or even gelatinous fluids. The intervening islands of renal parenchyma may be normal in appearance or may show secondary compression, atrophy, and fibrous arterionephrosclerosis, or pyelonephritis, resulting in eventual renal failure. Dissections of the nephrons and collecting ducts in such cases have shown that the cyst dilatations and proliferations occur in any part of the nephron but have a special predilection for the angle of Henle´s loop and Bowman´s capsule. 93. BENIGN NEPHROSCLEROSIS (Arterionephrosclerosis) Benign nephrosclerosis is the most common form of renal disease and is seen in most persons over 60 years of age. Long staining moderate arterial hypertension induces arteriosclerotic proliferative and hyaline changes of small muscular branches of the renal arteries and renal arterioles. These changes result in focal atrophy of tubules and sclerosis of glomeruli. The intervening kidney is relatively uninvolved, thus renal function is usually fairly well maintained. Microscopically the small muscular arteries show intimal thickening because of proliferation of intimal smooth muscle cells, which deposit new elastic fibres, the lamina of basement membrane, and collagen fibrils. Under the light microscopy this material has a pink hyaline appearance. Although some intimal thickening occurs with age, it is most striking when associated with hypertension. Under low magnification the most prominent feature is the thickened walls of larger arteries, particularly in the medulla of the kidney. Median magnification shows elastic-hyperplastic proliferation of the intima. The glomeruli are partially hyalinized and sclerosed, and their tubules are atrophic, with interstitial fibrosis and loose infiltration with lymphocytes. If several groups of glomeruli are hyalinized or sclerosed, atrophy of the tubular system and contraction of the fibrotic connective tissues lead to a depression on the surface of the kidney (arteriosclerotic scar). The beginner can easily mistake the arteriosclerotic scars and their lymphocytic infiltrates for chronic pyelonephritis. 94. MEMBRANOPROLIFERATIVE (MESANGIOCAPILLARY) GLOMERULONEPHRITIS Glomerulonephritis (GN) is an inflammation of the glomeruli. All glomeruli in both kidneys may be affected uniformly (diffuseGN) or only single may be involved (focal GN). The glomerular inflammation follows the general rules of an inflammatory process; exsudation denotes the leakage of blood plasma and agregation of granulocytes (exsudativeGN). Cellular proliferation may affect only the mesangium and the endothelium (mesangial and endocapillary, proliferative GN). In so-called membranous GN, the basement membrane is principally affected (thickened). Cellular proliferation is not significant. A combination of basement membrane thickening and cellular proliferation is found in membranoproliferative GN. In almost all forms of GN, immune complex can be demonstrated in the mesangium or on the basement membrane. On the basis, it is assumed that the basic pathogenic mechanism of GN is an antigen-antibody reaction. This mechanism then explains all the morphologic features. The group of glomerular diseases called ”membranoproliferative glomerulonephritis” is characterized by infiltration of inflammatory cells, by proliferation of intrinsic glomerular cells, and by altered structure and function of the glomerular basement membrane. Membranoproliferative glomerulonephritis, also known as ”mesangiocapillary glomerulonephritis”, occurs in 10 to 15% of patients with nephrotic syndrome and is most common in the second decade. The glomeruli by light microscopy are large and hypercellular and show distinctive club-shaped glomerular lobules. There is a striking increase in mesangial cells and mesangial basement membrane substance. The glomerular capillary walls are often double contoured from splitting of the basement membrane. Neutrophils are seen in these 93 tufts during peaks of clinical activity. Subendothelial and intramembranous complexes accompany proliferation of the mesangial cells. They overlie and intrude through the fragmented basement membrane into the periphery of the loops. 95. ACUTE PYELONEPHRITIS The etiology and pathogenesis of lower as well as upper urinary tract infection are interrelated. Most cases of acute pyelonephritis occur after infection of the lower tract. Escherichia coli is the cause of 85% of urinary tract infections. Other common pathogens are Proteus, Enterococcus and Pseudomonas. With reccurent acute attacs the latter organisms are more common and may be resistent to antibiotics. Clinically, lower tract infection is characterized by dysuria, higher frequency of wetting and bacteriuria. A swollen wedgeshaped area involving the papilla and adjacent cortex, infiltrated by gray-white foci of inflammatory reaction, characterizes grossly acute pyelonephritis in the absence of obstruction. Microscopically there are neutrophils in the tubules and in the edematous stroma. Microabscesses may be present. The glomeruli are relatively spared. The adjacent, uninvolved kidney is without lesions. With acute obstruction the process may spread to involve the kidney extensively and even produce necrosis of the renal papillae. 96. NEPHROBLASTOMA (Wilm´s tumor) Nephroblastoma, a malignant tumor that arises from metanephrogenic tissue, is the commonest solid abdominal tumor in children. Grossly nephroblastomas are bulky, spherical, deceptively circumscribed white or gray-white masses occasionally without focal haemorrhage, necrosis, or cyst formation. Histologically it is a mixed tumor with a sarcomatous stroma and pseudoglomerular and pseudotubular differentiated structures. The commonest pattern is a dimorphic distribution of sheets of undifferentiated immature cells resembling metanephric blastema and variously differentiated elements, tubules, abortive glomeruli, or even dysontogenetic tissue. Rapid local invasion and distant metastases, importantly to the lungs, are seen. 97. RENAL CELL CARCINOMA (Adenocarcinoma of kidney) This tumor comprises 70 – 80% of renal cancers. The designation ”hypernephroma” reflects an outmoded concept that they arise from ectopic adrenocortical cells. Renal adenocarcinoma usually occurs between 50 and 70 years of age and twice as common in men as in women. Metastases may occur early in a variety of sites. Prognosis depends on the extent of spread and the presence or absence of vascular invasion. The tumors are roughly spherical and are often large. They are often conspicuously yellow in colour and show central areas of haemorrhage, coagulative necrosis, and cystic excavation. This malignant tumor of the kidney consists of typical clear or plant cell-like cells. The tumor cells are arranged in an alveolar or trabecular or cystopapillar fashion and have a clear, optically empty cytoplasm (glycogen) and a rounded nucleus. The criteria for malignancy in hypernephroma are diameter greater than 3 cm, invasion of vessels or the renal pelvis, mitoses, atypia, and polymorphism (sarcomatous growth). 98. HYDRONEPHROSIS Mechanical obstruction to urinary outflow causes a rise of luminal pressure and proximal dilatation of the ureter (hydroureter) and renal pelvis (hydronephrosis). The cause of obstruction may be congenital anomalies, neuromuscular defects such as cord bladder, benign and malignant tumors, renal and bladder calculi, infection and subsequent fibrosis, and pregnancy. The prognosis of the process is determined by the degree and location of obstruction. With advanced hydronephrosis the renal parenchyma is stretched over the dilated caliceal system and undergoes intense fibrous atrophy of all components. When hydronephrosis is bilateral and early (acute), the kidney may show only moderate tubular dilatation and flattening and mild chronic interstitial inflammatory infiltrates. 99. BENIGN PROSTATIC HYPERPLASIA (”Hypertrophy”) 95 This is a hormonal hyperplasia of the periurethral prostate gland (so-called inner prostatic gland) accompanied by diffuse or nodular proliferation of smooth muscle fibres fibrocytes. The external prostatic gland (the source of carcinoma of the prostate) is displaced toward the periphery and forms so-called surgical capsule. Adenomatous hyperplasia is a disease of old men. Macroscopically, there is an enlargement of both lateral lobes and frequently a pseudomiddle lobe is formed. Under low magnification it is apparent that there is an increased number of glands and that they vary in diameter. Under higher magnification there are irregularly shaped lumina, the result of pseudopapillary evolution of the epithelial lining. These cells are cylindrical, with a basal nucleus and pale cytoplasm. The cell layer still consists of a single layer (the section must be examined carefully). The stroma contains elongated, eosinophilic muscle fibres and fibrocytes. Occasionally a prostatic nodule may have a purely leiomyomatous structure (its hard consistency may mimic a carcinoma clinically). The lumina of the glands contain an amorphous, eosinophilic material, inflammatory cells, and concentrically layered, occasionally calcified protein masses (corpora amylacea). 100. MUCINOUS CYSTADENOMA OF THE OVARY Mucinous cystadenoma is an benign epithelial tumor arising from the surface epithelium that is characterized by numerous cysts, filled with thick, viscous fluid. It is less often bilateral. Typical tumors of this type tend to grow to tremendous size, have a multilocular structure, and the cyst walls are as thin and translucent as tissue paper. The cysts are filled with soft gelatinous material. These tumors are benign and more often pedunculated than the papillary serous cystadenomas and often are removed more succesfully at operation. However, they may be bilateral or become implanted in the peritoneal surfaces and slow reccurence may take place, but malignant change is rare. Microscopically, a single layer of tall columnar epithelium lines the cysts. This typical ”picket – fence” epithelium, with clear, tall cytoplasm and basally placed nuclei, and the multilocular character of the cyst, and the mucoid fluid contents are diagnostic features of mucinous cystadenomas of the ovary. The gross specimen shows the multilocular character of the tumor on its uncut surface. The tense bulging lobules of the tumor, which are filled with mucinous fluid, are emphasized. The cut surface of the tumor shows the multilocular character of the cystic growth, the cystic cavities being lined by mucoid secreting tissue. The epithelium does not invade the wall and the serosa is intact. 101. SEROUS CYSTADENOCARCINOMA OF THE OVARY Serous cystadenocarcinoma is the most common malignant ovarian tumor arising from the surface epithelium, accounting for a third of all cancers of the ovary. In half of the pacients, the tumors are bilateral. Since tumors of advanced stage are bilateral more than twice as often as tumors of low stage, it is thought that in many cases the cancer spreads to the other ovary by implantation. On gross examination, serous cystadenocarcinomas usually present as multiloculated tumors, with soft, delicate papillae lining the entire surface. Solid areas, often with areas of necrosis and haemorrhage, are commonly present. Microscopically, serous cystadenocarcinomas vary from well differentiated to poorly differentiated tumors. In the latter, the papillary pattern may be inconspicious, with most areas being composed of solid sheets of malignant cells. Stromal and capsular invasion by the tumor cells is evident. Laminated calcified concretions, referred to as psammoma bodies, are present in one third of the cases. 102. ECTROPION OF THE CERVIX This is an eversion of the cervical mucosa at the cervical orifice. The cervical mucosa is very sensitive to mechanical and chemical stimuli, and its cylindrical epithelium is replaced gradually by squamous epithelium. This replacement may start from the periphery (ascending overgrowth) or may develop locally in the form of squamous metaplasia. A fully developed squamous overgrowth of pseudoerosion shows a multilayered, noncornified, squamous epithelium on the surface, covering the cervical glands. This interferes with the flow of secretions from the glands and retention cysts develop (Nabothian cysts). 97 103. CYSTIC GLANDULAR HYPERPLASIA OF THE ENDOMETRIUM Cystic hyperplasia is the result of hormonal imbalance, namely the increase and prolongation of estrogen production. The most common cause of such hyperestrogenism is the persistence of Graafian follicle of the ovary. This is seen frequently in premenopausal women over 40 years of age. In younger women similar changes can be seen in the first few periods after a precending pregnancy (so-called adaptation hyperplasia). In older menopausal women a hormone-producing ovarian tumor may be present. This is an estrogen-induced hyperplasia of the stroma and glands. The diagnosis is usually made from curetted material that consists of large fragments of tissue embedded in blood. Even the naked eye will reveal that there is abundant material and that some of the pieces are quite large. Under higherf magnification, it is apparent that the endometrium is in the proliferative stage and that the stroma is tightly packed with cells. The dominant feature of the field is cystic dilatation of the endometrial glands. These consist of a single layer of cylindrical epithelium. In addition to the intact epithelium, there are also smaller pieces of aglandular stroma and separated glands and epithelial cells. These findings correspond to menstrual material. It is of diagnostic significance if small, eosinophilic, homogenous, or very finely granular fibrin thrombi are found, since these represent morphologic evidence for a perfusion. 104. CARCINOMA OF THE UTERINE CERVIX After several decades as the most common gynecologic cancer, cervical carcinoma is now in most Western countries encountered less often than endometrial carcinoma. Invasive cervical carcinoma manifests in three somewhat distinctive patterns: fungating (or exophytic), ulcerating, and infiltrative cancer. The most common variant is the fungating tumor, which produces an obviously neoplastic mass that projects above the surrounding mucosa. Advanced cervical carcinoma extends by direct continuity to involve every contiguous structure, including the peritoneum, urinary bladder, ureters, rectum, and vagina. Distant metastasis occurs to the liver, lungs, bone marrow, and other structures. Histologically, 65% of tumors are large cell, nonkeratinizing, and moderately to well differentiated, 25% are large cell, keratinizing, producing keratohyalin, epithelial pearls, and pickle cells, and the rest are composed of small undifferentiated squamous cells. 105. CARCINOMA OF THE ENDOMETRIUM Endometrial carcinoma is common invasive cancer of the female genital tract and accounts for 7% of all invasive cancer in women (excluding skin cancer). At one time, it was far less common than cancer of the cervix, but earlier detection and eradication of in situ cervical cancer and an increase in endometrial carcinomas in younger age groups have reserved this ratio. Carcinoma of the endometrium is uncommon in women under age 40. The peak incidence is in the 55 to 65 year old women. Histologically, most endometrial carcinomas are adenocarcinomas characterized by more or less well-defined patterns lined by malignant stratified columnar epithelial cells. They may be well differentiated (grade 1), having a prominent, easily recognizable glandular pattern, moderately differentiated (grade 2), showing well-formed glands mixed with solid sheets of malignant cells, or poorly differentiated (grade 3), characterized by solid sheets of cells with barely recognizable glands and a great degree of nuclear atypia and mitotic activity. Most endometrial adenocarcinomas are well differentiated and composed of festoons and ribbons of collumnar epithelium, forming multiglandular masses. Strands of epithelium that lacks stroma support typically bridge the gland spaces. Nuclei are large and have irregular outlines, clumped chromatine, and prominent nucleoli. 106. SPONTANEOUS ABORTION The spontaneous abortion applies to a pregnancy that terminates before the fetus is capable of extrauterine life, which is about the 22nd week of gestation. The principal factors responsible for abortion are maternal, and fetal, and include the following: infection early in pregnancy, mechanical factors (e.g. submucous uterine leiomyoma or cervical incompetence), endocrine factors (e.g. inadequate progesterone production), immunologic factors, and fetal congenital and chromosomal abnormalities. Histologically, the aborted material shows secretory endometrium with decidual reaction of the stroma and placental villi. Frequently, there is also marked infiltration of 99 polymorphonuclear leukocytes which are a response to disintegration and separation of the endometrium. In the endometrium, there are corkscrew shaped glands having irregular lumen. The gland epithelium has a pale cytoplasm and the nuclei are at the base. Decidual cells are large stromal cells having distinct borders, abundant clear (glycogen-containing) cytoplasm, and a round centrally placed nucleus. The presence of placental villi is histologic evidence of abortion. The villi are composed of a delicate, cell-poor stroma containing capillaries. The surface of the placental villi consists of an inner layer of cuboidal cells (cytotrophoblast – Langhans’ cells) and an outer layer of large multinucleated giant cells without definable borders (syncytiotrophoblast). 107. HYDATIDIFORM MOLE Hydatidiform mole is characterized by grossly swollen chorionic villi, resembling bunches of grapes, accompanied by variable trophoblastic proliferation. It is the most common precursor of choriocarcinoma. Two types of noninvasive moles can be differentiated: complete and partial. In contrast to complete moles, partial moles are rarely followed by choriocarcinoma. The uterus is usually larger than anticipated for the duration of pregnancy. The uterine cavity is filled with a friable mass of thin-walled, translucent, cystic, grape-like structures. Microscopically, the complete mole shows hydropic swelling of chorionic villi which appear avascular with routine staining. The villi are enlarged and round, and many of them have cisternae, which are central, acellular fluid-filled spaces devoid of mesenchymal cells. The trophoblast composed of syncytiotrophoblast, cytotrophoblast and intermediate trophoblast is diffusely hyperplastic and displays considerable cellular atypia. In partial moles, dual population of villi is observed, i.e. some of them are enlarged by hydropic swelling, may show central cavitation and have irregularly scalloped contours, whereas others show only minor changes. The trophoblastic proliferation is usually more focal and mild than in complete moles. Typically, blood vessels are found within the chorionic villi and contain fetal (nucleated) erythrocytes. 108. SUPPURATIVE SALPINGITIS Salpingitis typically results from ascending infections of the lower genital tract. The most common causative organisms are N. gonorrhoeae, E. coli as well as streptococci, staphylococci, Chlamydia and Mycoplasma. Typically, the infection is polymicrobial. Uncommonly, salpingitis is a primary infection within the fallopian tube or represents a secondary spread of infection from a nearby perforated viscus, such as the appendix. In acute salpingitis, the lumen fills with purulent exudate. In the course of days or weeks, the tubal fimbriae may seal or become plastered against the ovary to create a salpingo-oophoritis and tubo-ovarian abscess. Pus may collect in these sealed tubes to cause distention (pyosalpinx). The infection tends to smoulder and becomes chronic for months and even years. The pus may be transformed to a thin, serous fluid (hydrosalpinx). Other complications of salpingitis are: peritonitis, fibrous adhesions between the serosa of the tube and surrounding peritoneal surfaces, infertility and ectopic pregnancy. Microscopically, the tubal serosa becomes hyperemic and layered with fibrin. The tubal fimbriae are similarly involved, the lumen fills with purulent exudate and mucosal folds (plicae) show marked edema, congestion and presence of inflammatory infiltrate of polymorphonuclear leukocytes. The inflammatory infiltrate in chronic salpingitis is composed mostly of lymphocytes and plasma cells, and edema and congestion tend to be minimal. 109. TUBAL PREGNANCY WITH ABORTION Ectopic pregnancy refers to any implantation of the fertilized ovum that develops outside the endometrium. The most common location is within the fallopian tubes. Tubes which are fibrosed as a result of chronic inflammation or which are congenitally abnormal may prevent the passage of the ovum. The retained ovum may undergo fertilization and implant itself in the wall of the tube to constitute an ectopic (tubal) pregnancy, which may cause life threatening tubal rupture and intraperitoneal hemorrhage. The tube is expanded by blood clot (hematosalpinx). The muscle of the tubal wall is hyperemic and edematous. Mucosal folds may be observed or they may be replaced by welldeveloped decidua. Blood clot in ihe lumen contains chorionic villi composed of a myxoid core and trophoblast being on the surface. Sheets of trophoblast as well as decidual tissue may be found lying free in the lumen. Fetal elements may or may not be found among the contents 101 of the tube. 110. FIBROCYSTIC DISEASE (FIBROCYSTIC CHANGES) OF THE BREAST Fibrocystic disease of the breast refers to a constellation of morphologic features characterized by (1) cystic dilatation of terminal ducts, (2) relative increase in fibrous stroma, and (3) variable proliferation of terminal duct epithelial elements. The cause of fibrocystic change is unknown. The forms of fibrocystic disease (FD) that do not carry an increased risk for the development of cancer (termed non-proliferative FD) are far more prevalent. Some of the florid manifestations appear to be indicators for women at increased risk for breast cancer. Such lesions are designated proliferative FD. A less common variant is known as sclerosing adenosis. Nonproliferative (simple) FD is usually multifocal and often bilateral. The morphologic hallmarks are an increase in dense fibrous stroma and some degree of cystic dilatation of the terminal ducts. Cysts are of various sizes. In smaller ones, the epithelium is more cuboidal to columnar and sometimes multilayered. In larger cysts, it may be flattened or totally atrophic. Frequently, cysts may be lined by large polygonal cells having an abundant granular, eosinophilic cytoplasm with small, round, deeply chromatic nuclei (so-called apocrine metaplasia - cells resemble apocrine sweat gland epithelium). These cells are usually arranged in single layer but on occasion they form papillary structures. Proliferative FD or epithelial hyperplasia is the proliferation of epithelial cells which causes an increase in the layers of the duct-lining epithelium beyond the usual double layer sometimes resulting in a mass obliterating the lumens. Proliferations may sometimes show architectural and cellular abnormalities and then they are called the atypical hyperplasia. Sclerosing adenosis is characterized by proliferation of small ducts and myoepithelial cells (adenosis) and the lesion is commonly associated with fibrosis (hence the term sclerosing). 111. INVASIVE LOBULAR CARCINOMA OF THE BREAST Invasive lobular carcinoma probably arises from the terminal ductules of the breast lobules. It tends to be bilateral and multicentric within the same breast. Grossly, the presentation of the tumor varies from a discrete firm mass to a more subtle, diffuse, indurated area according to the amount of fibrosis produced. Histologically, it consists of strands of infiltrating tumor cells, often in linear arrangement, only one cell in width (in the form of an "Indian file"), loosely dispersed throughout the abundant fibrous matrix, or appear individually embedded in this fibrous tissue. The cells are small and uniform-staining with relatively little pleomorphism. Irregularly shaped, solid nests and sheets may also occur. The tumor cells are frequently arranged in concentric rings (target-like pattern) about normal ducts. Identification of remnants of lobular carcinoma in situ aids in the diagnosis. In invasive carcinomas of breast, thick bands of eosinophilic material surrounds non-malignant ducts which is composed of elastin (elastosis). 112. HASHIMOTO´S THYROIDITIS Hashimoto´s thyroiditis (HT) also termed lymphocytic (lymphadenoid) goiter or struma lymphomatosa is an autoimmune disease characterized by the presence of circulating antibodies to thyroid antigens. The basic defect is thought to be a genetically (certain HLA antigens are commonly found in affected individuals) conditional deficiency in the function of thyroid-specific supressor T cells. As a consequence there is uncontrolled attack on the follicular cells by cytotoxic T cells, and simultaneously, the cooperation of helper T cells with B cells in the thyroid to produce a constellation of autoantibodies. Grossly, the thyroid in classic goitrous form is characterized by diffuse, moderate enlargement and appears firm, fleshy and pale. Little or no glandular enlargement is seen in less common atrophic variant and in some instances, the fibrosis produces a reduction in thyroid size. Histologically in the goitrous form, the gland is densely infiltrated by lymphocytes and plasma cells, with lymphoid follicle formation with germinal centers. Many thyroid follicles disappear. Those remaining are irregular in size and shape, some consisting only of clusters of epithelial cells. Others are lined by cells which show a characteristic change: they enlarge and develop eosinophilic granular cytoplasm due to proliferation of mitochondria (Hürthle cells, oncocytes or Askanazy cells). Very little colloid is present. Atrophic variant reveals much more abundant fibrosis with a commensurate decrease in the lymphoid infiltrate. 103 113. COLLOID GOITER OF THE THYROID The term goiter denotes an enlargement of the thyroid in excess of the normal weight for adults of 25 - 50 g. Hyperplastic changes, which are associated neither with functional alterations nor with producing nodularity, are known as the diffuse nontoxic (simple) goiter and include parenchymatous and colloid goiter. Simple goiter occurs in both endemic and sporadic distribution. Nearly all long-standing simple goiters become transformed into multinodular goiters. They may be nontoxic or may induce thyrotoxicosis. Grossly, the gland tends to be soft, glistening, and yellow. Necrotic, fibrotic, hemorrhagic and cystic areas are common. Calcific foci, which impart a gritty surface, are frequent. Microscopically, there are follicles seen in the thyroid, which are of various sizes and accumulate large amount of colloid observed as eosinophilic substance within the follicles. They may coalesce to form colloid-filled cysts. The epithelial cells lining the follicles are flat and so-called resorption vacuoles can be seen near the surface of the epithelial cells. There may be also seen the areas of hemorrhage, fibrosis and dystrophic calcification. 114. PITUITARY ADENOMA Pituitary adenomas are benign neoplasms of the anterior lobe of the pituitary gland. They may be derived from any of the hormone-secreting cells and thus may be clinically manifested by virtue of single hormone overproduction, destruction of surrounding normal pituitary and consequent hypofunction, and mechanical effect due to intracranial pressure rise and specific location (pressure effect on the overlying optic chiasma). Pituitary adenomas were subdivided according to the tinctorial properties of their cells. Thus, they were classified as acidophil, basophil or chromophobe adenomas. Pituitary adenomas are today classified according to the hormone(s) elaborated by the neoplastic cells, and this can be demonstrated by immunohistochemical methods, or by EM. Microscopically, all adenomas have a fairly uniform appearance. The more or less uniform polygonal cells are arranged in sheets, cords, or nests, having only a delicate, vascularized stroma. Sometimes, pseudoglandular or papillary formations are present. Small or large foci of ischemic necrosis may be present, and psammoma bodies may be found, accompanied by hemorrhage. Some adenomas, usually those that grow more rapidly, have some variation in cell and nuclear size and shape. The cytoplasm may be eosinophilic or basophilic due to presence of granules of various natures. Cells of chromophobe adenoma mostly do not contain visible granules. Basophil adenoma stains darkly and reacts strongly with the PAS stain. A distinctive alteration, referred to as Crooke´s hyaline change, may be seen in the cells. 115. PARATHYROID ADENOMA Parathyroid adenoma accounts for more than a half of all cases of primary hyperparathyroidism. The tumor is a circumscribed, reddish-brown, solitary mass, measuring 1 to 3 cm in diameter. Appearance of cut surface is uniform, and cystic changes are occasionally noted. On microscopic examination, parathyroid adenoma is composed of sheets of neoplastic cells embedded in a rich capillary network. For the most part, the cells resemble normal chief cells, but some water-clear and occasional oxyphilic foci may be present. In some instances, bizarre, multinucleated cells and other atypical nuclear and cytoplasmic features are noted. On occasion, the neoplastic cells are arranged in pseudorosettes around blood vessels or as follicles containing eosinophilic, colloid-like material. A rim of normal parathyroid tissue should be evident outside the capsule and serves to distinguish an adenoma from parathyroid hyperplasia. 116. FIBROUS CORTICAL DEFECT (Nonossifying fibroma of the bone) Fibrous cortical defects are extremely common non-neoplastic developmental defects being found in 30 to 50 % of all children older than two years. They occur in the metaphyses of long bones, most frequently the tibia or femur. They create irregular, sharply demarcated, lobular, radiolucent defects in the metaphyseal cortex with an intact shell of overlying bone. The margins of these lesions are sometimes slightly sclerotic. They are generally 105 asymptomatic, but larger ones may cause pain and predispose to fracture. They often disappear spontaneously within a few years. On gross examination, the lesion is granular and dark red to brown. Microscopically, almost uniform spindle cells (fibroblasts, which sometimes form palisades) are arranged in an interlacing, whorled pattern, in which multinuclear giant cells and foamy macrophages may be seen. There is no evidence of bone formation. The color of the lesion is caused by hemosiderin, which is present in macrophages. 117. PYOGENIC OSTEOMYELITIS Pyogenic osteomyelitis almost always is caused by bacteria, rarely by fungi. The organisms may reach the bone (1) through the bloodstream (in most cases), or (2) locally by direct extension of a contiguous infection and by direct traumatic (including surgical) introduction. Almost any pathogen may be responsible, but most often implicated is Staphylococcus aureus and less frequently E. coli, Pseudomonas, Klebsiella or other pyogens. In hematogenous osteomyelitis, the reactions usually begin in the metaphyseal marrow. Pus may spread in the medullary cavity and beneath the periosteum. Considerable necrosis of bone is liable to occur in osteomyelitis, often through damage to the blood supply. Histologically, the medullary cavity is full of pus and the collections of polymorphonuclear leukocytes replace the original marrow. The trabeculae of spongiosa are necrotic and the bony lamellae are in the process of disappearing. The lacunae are empty, without osteocytes. Necrotic bone tissue may form a sequestrum. Sometimes the bacterial colonies as finely granular basophil material may be seen in the exudate. Over time, the host response evolves including osteclastic bone resorption, ingrowth of fibrous tissue and deposition of reactive bone in the periphery. 118. OSTEOSARCOMA Osteosarcoma is a highly malignant mesenchymal tumor characterized by the formation of neoplastic bone tissue, i.e. osteoid or bone. Osteosarcoma is most frequent in adolescents between the ages of 10 and 20 years and often arises in the vicinity of the knee, although any area of a long bone may be affected. The gross appearance of the tumor is highly variable, depending on the relative amounts of bone, cartilage, stroma and blood vessels. The tumor invades the medullary cavity and expands the periosteum, sometimes breaking through it. The cut surface may show any combination of hemorrhagic, cystic, soft, and bony hard areas. It metastasizes readily by the bloodstream to the lungs and the prognosis is poor. Histologic examination reveals malignant pleomorphic osteoblasts varying considearbly in size and shape and frequently having large hyperchromatic nuclei. Bizarre tumor giant cells are common, as are mitoses, which are often atypical. The most characteristic feature of osteosarcoma is formation of osteoid and bone. It has a coarse lace-like architecture but is also deposited in broad sheets or as primitive trabeculae. Neoplastic tissue contains many vessels and vascular invasion is usually conspicuous. Malignant cartilage and fibrous tissue may be present in varying amounts. Neoplastic osteoid and bone predominate in welldifferentiated osteosarcoma which is relatively hypocellular. In the teleangiectatic variant, the majority of the tumor is composed of blood-filled cysts, and the tumor cells reside in the cyst walls. 119. DENERVATION ATROPHY OF SKELETAL MUSCLE The pathology of denervation reflects lesions of the lower motor neuron. Denervation atrophy results from damage to the muscle innervation. This can occur as a consequence of lesions affecting motor neurons, nerve roots or peripheral nerves. When a skeletal muscle fiber becomes separated from contact with its lower motor neuron, it invariably atrophies. The pattern of denervation does not identify the cause of the lesion. On cross section, the atrophic fibers have a characteristic angular configuration being compressed by surrounding normal muscle fibers. Intact fibers and denervated ones may lie side by side. Some loose connective tissue may be between them and there may be an infiltrate of fat associated with the denervated fibers, which are atrophic and narrow. As the disease progresses, these fibers are seen in groups, at first in small clusters of several fibers, and later in larger groups or the whole fasciculi. Sarcolemmal nuclei appear to have increased number because of the shrinkage of the fibers. If the fiber is not reinnervated, the atrophy proceeds to complete loss of myofibriles and myofilaments, and the nuclei condense into aggregates. 107 120. NONSUPPURATIVE MYOSITIS There is a variety of inflammatory diseases involving muscle, including infectious myositis, noninfectious inflammatory muscle disease (inflammatory myopathies), and inflammatory processes associated with diffuse systemic inflammatory diseases. Three major inflammatory myopathies (they are thought to have an autoimmune origin) are recognized, namely polymyositis, dermatomyositis and inclusion body myositis. At the onset, the muscles are normal in gross appearance, possibly slightly enlarged owing to diffuse edema. With advance of the disease, they become atrophic and yellowish-grey as the muscle fibers are replaced by fibrous tissue and fat. Histologically, the most prominent characteristics are the presence of inflammatory mononuclear cells around small blood vessels, in the perimysial conective tissue or in the endomysium; degeneration manifested by granular change, vacuolar degeneration, increased eosinophilia, fragmentation and simple necrosis of the muscle fibers sometimes accompanied by phagocytosis and ”ghost fiber” (unstained muscle fiber) formation; a mixture of atrophic and regenerating fibers producing large vesicular sarcolemmal nuclei increased in number and accompanied by sarcoplasmic basophilia; and fibrosis. 121. SUBACUTE SCLEROSING PANENCEPHALITIS Subacute sclerosing panencephalitis (SSPE) is a viral infection of the brain caused by measles virus and generally occurs in children but can be seen in adolescents and young adults. It has always been preceded by an attack of measles in the distant past, often usually early in life, or, occasionally, by previous immunization against measles. SSPE usually starts with personality and behavior changes, followed by the development of involuntary movements and sensory deficits, and ultimately causes stupor and death, all over a period of several years. In tissue sections, the inflammation is highlighted by the presence of prominent intranuclear eosinophilic or amphophilic inclusions within neurons, oligodendroglia and astrocytes; ubiqitous perivascular cuffs of lymphocytes, plasma cells and few macrophages; patchy loss of myelin; extensive neuronal loss and neuronophagia and there is marked fibrillary astrogliosis in damaged areas in both the grey and white matter (accounting for the term sclerosing). 122. HEALED INTRACEREBRAL HEMORRHAGE The most important predisposing factor for intracerebral hemorrhage is arterial hypertension. Other associated conditions include intracerebral arteriovenous malformations, tumor, hemorrhagic diathesis, and amyloid angiopathy. The hematoma acts as a space-occupying lesion causing a rapid increase in intracranial pressure and herniation. In survivors, resorption of the hematoma eventually occurs, and over period of months a fluid-filled cavity with a gliotic wall is formed. The wall remains brown-pigmented for years and thus, suggests the origin of the cavity. Microscopically, resolution of a hemorrhage begins with appearance of macrophages that digest the blood clot. The erythrocytes and hemoglobin are taken up by phagocytes and broken down to hemosiderin and hematoidin. The phagocytes can be seen as granular fatty cells like those in the brain white infarction but most of macrophages are called pigmented granular cells, since cytoplasm contains brown hemosiderin granules. Eventually, a slit-like pseudocyst (a cavity without the epithelium lining the wall) surrounded by a zone of fibrillary astrocytosis containing scattered hemosiderin-laden macrophages and extracellular deposits of yellow-brownish pigment (hematoidin). 123. OLIGODENDROGLIOMA The oligodendroglioma is derived from oligodendrocytes. It is most common in middle life and arises mostly in the cerebral hemispheres, with a predilection for white matter. Grossly, oligodendrogliomas are well-circumscribed grey masses, often with cysts, focal hemorrhage and calcification. Microscopically, the structure is characteristic. The tumor is highly cellular and is composed of sheets of regular cells. They have small round nuclei surrounded by a clear halo of cytoplasm bounded by a well-defined cell membrane. Typically, a delicate network of capillaries separates the tumor cells into clusters. The calcification, which is present in up to 90% of these tumors, ranges from microscopic foci to massive depositions. The slow growth 109 is reflected in an absence of mitotic figures and necrosis. 124. MENINGIOMA Meningiomas arise from meningothelial cell of the arachnoid. They may be found along any of the external surfaces of the brain as well as within the ventricular system, where they arise from the stromal arachnoid cells of the choroid plexus. The most frequent sites are the parasagittal region, convexities of the cerebral hemispheres, the olfactory groove, and the lateral wing of the sphenoid. Grossly, meningiomas are usually irregular, well-circumscribed bosselated masses firmly adherent to the dura that indent the surface of the brain but rarely invade it. The cut surface presents a gray, whorled pattern. Histologically, several patterns have been recognized. The histologic hallmark of syncytial type is the whorled clusters of cells which sit in tight groups without visible cell membranes. Fibroblastic meningiomas have spindle-shaped bipolar cells that resemble fibroblasts arranged in bands and swaths. Transitional types share features of the syncytial and fibroblastic types. Psammomatous type has a dominant pattern of psammoma bodies, which result from hyalinization and calcification of the syncytial whorl centers. PAS-positive intracytoplasmic droplets and intracellular lumina by electron microscopy are seen in secretory type. Microcystic type has a loose, spongy appearance. Some meningiomas are dominated by blood vessels (angioblastic meningiomas), others have a papillary appearance (papillary meningiomas). The latter variant is composed of pleomorphic cells arranged around fibrovascular cores and is associated with a worse prognosis. In addition, various forms of degeneration can be seen in meningiomas, including xanthomatous and myxomatous degeneration and bone and, rarely, cartilage formation. 125. PILOCYTIC ASTROCYTOMA Astrocytoma is tumor of glial origin composed of astrocytes. Pilocytic astrocytomas are distinguished from other astrocytomas by their distinctive pathologic appearance and almost invariably benign behavior. They typically occur in children and young adults and usually are located in the cerebellum, but may also appear in the floor and walls of the third ventricle, the optic nerves and, occasionally, the cerebral hemispheres. Grossly, pilocytic astrocytoma is often cystic, with the tumor confined to a mural nodule in the wall of the cyst, but if solid, it may be well circumscribed or, less frequently, infiltrative. Microscopically, the tumor is only moderately hypercellular and is composed of pilocytic astrocytes, which are bipolar cells with long, thin ”hair-like” processes. Rosenthal fibers (eosinophilic, opaque, elongated, tapering or globular bodies that form in astrocyte processes) and microcysts are often present. Vascular endothelial proliferation is also common, but in this tumor, unlike in the other astrocytomas, it does not imply an unfavorable prognosis. Necrosis and mitoses are almost never present. 126. GLIOBLASTOMA MULTIFORME Glioblastoma multiforme is a highly malignant tumor of glial origin, which shows the extreme expression of anaplasia among the glial neoplasms. This tumor is the most common glial neoplasm. It is distinguished from the other types of glial tumors by its variegated appearance, hence the term multiforme. Glioblastoma multiforme occurs mostly in white matter of cerebral hemispheres and typically infiltrates extensively, frequently crossing the corpus callosum and producing a bilateral lesion likened to a butterfly in its gross configuration. Some regions may be white and firm, others yellow and soft and foci of necrosis, cysts and recent or remote hemorrhage are common. The cardinal histologic features of glioblastoma multiforme are as follows: marked cellularity, with variable degrees of cellular pleomorphism and multinucleated cells; serpentine areas of necrosis, which may or may not have pseudopalisading (zones of crowded tumor cells) around it; and proliferation of endothelial cells, which may form tufts bulging into the vascular lumen, referred to as ”glomeruloid” formations. 127. BENIGN FIBROUS HISTIOCYTOMA OF THE SKIN Benign fibrous histiocytoma (also known as subepidermal nodular fibrosis, dermatofibroma, histiocytoma, and sclerosing hemangioma) refers to a spectrum of firm, nodular, nonencapsulated, often pigmented lesions that occur chiefly on the extremities. Clinically, they may be single or multiple and have a flat polypoid or depressed shape. Most of them are less than 1 cm in diameter, but some can reach huge proportions. When heavily 111 pigmented, they may be confused clinically with nevi, malignant melanoma, Kaposi’s sarcoma, and other vascular tumors. On transection, they are usually solid and rather well circumscribed but not encapsulated, the color ranging from white to yellow to dark brown, depending on the relative amounts of fibrous tissue, fat, and hemosiderin. The behavior of this lesion is benign; local recurrence is rare even if the excision contains little normal tissue around the lesion. Microscopically, the papillary and reticular dermis are replaced by fibrous tissue with a distinctive pattern. There is a cellular fibroblastic proliferation with varying amounts of collagen deposition, admixed with a variable number of macrophages, most of which contain fat (thereby acquiring a foamy appearance) or hemosiderin. Some of these histiocytes are multinucleated and may acquire the features of Touton’s giant cells. The fibrohistiocytic proliferation is set in a fine vascular network, which can be very prominent (this vascular component is responsible for this lesion having been regarded in the past as a sclerosing hemangioma). Focal storiform features may be seen: the fibroblasts tend to form ill-defined small cartwheel patterns with a small vascular space at the center and thus the curved bundles of cells and tissue produce a basket-weave pattern. The lesion is characteristically centered in the upper dermis, but it can involve the deep dermis and occasionally extend into the subcutis. The tumors are not sharply circumscribed or encapsulated and blend imperceptibly into the adjacent dermis. The overlying epidermis can be normal, atrophic, or hyperplastic with elongation of hyperpigmented rete ridges. 128. ECZEMATOUS DERMATITIS (Eczema) Eczema is a clinical term that embraces a number of pathologically different conditions. All are characterized by red, papulovesicular, oozing and crusted lesions early on that with persistence eventuate into raised, scaling plaques. If untreated, the lesions will tend to become chronic. There are many causes of eczema and histological features tend to be the same irrespective of the cause. Histologically, the main features are edema within the epidermis (spongiosis), with separation and disintegration of clumps of epithelial cells to form vesicles. The dermal papillae are swollen and edematous and their blood vessels are dilated. There is an infiltrate of small lymphocytes in both the dermis end epidermis. Mast cells may be found in the inflammatory infiltrate, which, depending on the cause, may be rich in eosinophils. With time (days to weeks), the acute vesicular phase of spongiotic dermatitis may subside, giving rise to progressive epidermal hyperplasia (stratum spinosum thickens – a condition known as acanthosis) with hyper- and parakeratosis. 129. CONDYLOMA ACUMINATUM Condylomata acuminata are circumscribed, exophytic, cauliflower-like, fibroepithelial benign lesions that chiefly occur in the perianal and periurethral regions, or on the penis or external female genitalia. They are associated with sexually transmitted infection by HPV type 6 and less commonly type 11. They consist of single or multiple sessile or pedunculated, red papillary excrescenses that vary from 1 to several milimeters in diameter. Histologically, a branching, villous, papillary connective tissue stroma is covered by squamous epithelium of variable thickness and exhibits conspicuous acanthosis, hyperkeratosis and parakeratosis. Characteristic finding of koilocyte (an epithelial prickle cell with a perinuclear clear halo of cytoplasm and a wrinkled nucleus) is interpreted as evidence of HPV infection. The basal stroma is inflamed and vascular. Importantly, no significant cell atypism is present and the lesion is not a precursor of squamous cell carcinoma. 130. LUPUS ERYTHEMATOSUS OF THE SKIN Lupus erythematosus (LE) is an autoimmune disease affecting connective tissue. In many cases of LE the skin is the only organ involved and the disease is then called discoid LE. The systemic variant may or may not involve the skin but in any case is called systemic LE. The skin lesions are erythematous, scaly and indurated in the acute forms and slowly progress to atrophic scarred patches, often with hyperpigmented edges in the older lesions. They are often symmetrical on the face in a butterfly distribution over the nose and cheeks, and on the scalp may be associated with scarring alopecia. The scales can often be picked off and are shaped like tin-tacs. Histologically, the epidermis is thin, with a very atrophic stratum spinosum. There is hyperkeratosis, which extends down into the hair follicles, with the formation of follicular 113 plugs (tin-tacks). The basal layer of epidermis shows liquefaction degeneration. The dermis is edematous and hyaline, and there are deposits of eosinophilic fibrin in it. Beneath the damaged dermis there is a very intense infiltrate of chronic inflammatory cells, predominantly lymphocytes. The infiltrate is concentrated around dilated blood vessels and hair follicles. The infiltrate also involves the dermo-epidermal interface and damages the melanocytes. The melanocytes lose their melanin to dermal macrophages in which the melanin accumulates, accounting for the hyperpigmentation in older lesions. 131. SCLERODERMA (Progressive systemic sclerosis) Scleroderma, or the more contemporary term progressive systemic sclerosis (PSS), is an autoimmune disease of connective tissue characterized by excessive collagen deposition in the skin and internal organs. Scleroderma which is manifested by thickening of the dermis, begins on the fingers, later it involves the face and eventually, the skin over large parts of the body is thickened and stiff. The taut skin restricts movements. Histologically, there is distinct thinning of the epidermis along with the loss of rete pegs. The underlying dermis is poorly cellular and contains bundles of numerous thick and hyalinized collagen fibers. A patchy lymphocytic infiltrate with a few plasma cells is common. Sweat glands may be entrapped in the thickened fibrous tissue, and hair follicles are completely lost. 132. SQUAMOUS CELL CARCINOMA OF THE SKIN Squamous cell carcinoma (SCC) arises from the stratified squamous epithelium of skin, mucous membrane and also from areas of squamous metaplasia in other types of epithelium. SCC of the skin is very common and is etiologically related to chronic sunlight exposure or to chemical carcinogens. SCC may form roughened keratotic areas, ulcers or horns. Although they show obvious invasion, their behavior is usually fairly indolent and metastasis, when it occurs, is a late and relatively uncommon complication. Histologically, squamous cell carcinomas are composed of disorganized keratinocytes which appear to echo the behavior of the normal upper layers of the epidermis but in a disordered and malignant fashion. Neoplasms exhibit variable differentiation, ranging from tumors formed by polygonal squamous cells with pink, plate-like cytoplasm and intercellular bridges comprising desmosomes, and large zones of keratinization seen as ”epithelial pearls” to neoplasms formed by highly anaplastic, rounded cells with foci of necrosis and only abortive, single-cell (monocellular) keratinization (dyskeratosis). The stroma is infiltrated with lymphocytes and plasma cells. 133. HIDRADENOMA Hidradenoma is a benign neoplasm of the sweat glands. Papillary hidradenoma arises from the apocrine sweat glands and it appears chiefly in the labia majora of the vulva as a sharply circumscribed nodule, rarely larger than l cm. The tumor is demarcated from the adjoining tissues by a capsule of compressed dermal connective tissue. Within the tumor, one observes tubular and cystic structures. Papillary folds having a well-formed fibrous stroma project into the cystic spaces. The lumina are lined occasionaly with only a single row of columnar cells, which show an oval, pale-staining nucleus located near the base, a faintly eosinophilic cytoplasm, and active decapitation secretion as seen in the secretory cells of apocrine glands. Usually, however, the lumina are surrounded by a double layer of cells consisting of a luminal layer of secretory cells and of an outer layer of small cuboidal cells with deeply basophilic nuclei. These are myoepithelial cells. 134. NEUROFIBROMA OF THE SKIN Neurofibromas are benign tumors of peripheral nerves derived from Schwann cells. They may be solitary or multiple and may arise on any nerve. The presence of multiple neurofibromas is diagnostic of neurofibromatosis (type 1 of it is known as von Recklinghausen´s disease). Cutaneous neurofibromas present as soft, nodular or pedunculated skin tumors. The cut surface is soft and light gray. 115 Histologically, the lesion is generally well-circumscribed and usually unencapsulated. It consists of spindle cells with elongated slender nuclei, eosinophilic cytoplasm, and indistinct cell borders. The spindle cells often aggregate to form tiny strands coursing haphazardly through the tumor. Interspersed among the spindle cells are wavy bands of collagen, an extracellular loose myxoid matrix, and residual nerve fibers (but they require special stains for their demonstration). 135. CHORIOAMNIONITIS Chorioamnionitis refers to inflammation of the placental amnion and chorion and the extraplacental membranes. It is usually the result of an ascending infection from the maternal birth canal, most commonly owing to premature rupture of the membranes. The amniotic fluid is usually cloudy and contains purulent exudate. The membrane walls are slightly opaque, edematous, and friable. With more extensive spread the umbilical cord may become infected (funisitis) and exhibit acute vasculitis of one or more umbilical vessels or inflammation of the cord mesenchyma (Wharton’s jelly). Polymorphonuclear leukocyte infiltration is seen initially in the extraplacental membranes related to the cervical os. Neutrophils permeate the trophoblastic layers (stage 1). The next more advanced stage is where neutrophils have infiltrated into spongy layer of the amnion (stage 2). In stage 3, all layers of the amnion are involved, but the epithelium is preserved, and in in stage 4, necrotizing inflammation has destroyed the amnion. The chorioamnion of the placenta shows edema and congestion of the vessels. The inflammatory infiltrate involves the adjacent intervillous spaces as well where the polymorphonuclear leukocytes become enmeshed in fibrin. Spread of inflammation into the vessels and Wharton’s jelly of the umbilical cord (funisitis) is seen in the established cases. 136. AMNIOTIC FLUID ASPIRATION IN THE LUNG Fetal lung secretes a liquid that occupies the terminal air spaces and airways and whose composition and viscosity are different from those of the plasma and amniotic fluid. Normal breathing movements in utero are insufficient to clear the tracheal dead space, and therefore the tidal volume is very small. It is under various adverse conditions, that relatively large volumes of amniotic fluid may be inspired by the fetus. Aspiration of amniotic fluid occurs during premature respiration when intrauterine stress cause the infant to make a deep respiratory movement, and concomitantly, to pass meconium into the amniotic fluid. Aspiration may result in death or the meconium aspiration syndrome of the newborn. Microscopically, the air passages contain desquamated squamous epithelial cells (usually without nuclei) and lanugo hair from the fetal skin and eosinophilic protein-rich amniotic fluid. Squamous cells can be observed as large, flat squames or, they appear elongated, spindle-shaped strips, when cross-sectioned. Lanugo hair is seen as pale, cylinderlike structures. Typical finding is the presence of small round golden-brown (due to presence of bilirubin) bodies known as meconium bodies (probably desquamated colonic cells of the fetus). 137. HYALINE MEMBRANE DISEASE IN NEWBORN (Respiratory distress syndrome) Idiopathic respiratory distress syndrome (IRDS) also known as hyaline membrane disease is particularly liable to affect premature infants. 24 - 72 hours after birth, the child develops dyspnea and cyanosis. The cause is a deficiency of surfactant secretion by the type II pneumocytes. The child´s respiratory movements then fail to keep the alveoli fully expanded, with subsequent exudation of plasma protein (due to capillary damage) into the air spaces. The lungs are heavy, purple and solid, and sink in water. Histology shows alternating atelectasis and dilatation of the alveoli. Within expanded air spaces, proteinaceous edema fluid, and erythrocytes are evident. The alveoli, alveolar ducts or bronchioli are lined by conspicuous band of amorphous eosinophilic hyaline material consisting of polysaccharides, proteins and lipids. These substances come from necrotic alveolar cells and plasma proteins particularly fibrin. The walls of the collapsed alveoli are thick, the capillaries are congested, and lymphatics are filled with proteinaceous material. 138. PERINATAL PNEUMONIA Perinatal pneumonia also called intrauterine or congenital pneumonia is ussually referred to as pneumonia occuring within 48 hours of birth. Most intrauterine pneumonia is 117 the result of infection ascending from the birth canal into the amniotic sac. It is associated with premature rupture of the membranes and aspiration of infected amniotic fluid in utero. Perinatal pneumonia may be caused by infection acquired during passage through the birth canal (intrapartal infection) as well. Intrauterine pneumonia has been also observed in prolonged labor with intact membranes and in the remaining cases, infection is transplacental. Histologically, the pneumonia is usually diffuse and distal airways are filled with a polymorphonuclear inflammatory exudate, which may or may not contain squames as a result of amniotic fluid aspiration. The most striking feature is the absence of fibrin. The alveolar septa, bronchioles, and bronchi may be involved as well. Bacteria are not usually observed in sections, and if present, are few. 139. PNEUMOCYSTIS PNEUMONIA Pneumocystis pneumonia is a pulmonary infection with a protozoan organism called Pneumocystis jiroveci (carinii). It is an example of opportunistic infection (caused by an organism which is not pathogenic in the normal individual, but cause the infection in a pacient with immunodeficiency). It occurs in prematurely born and malnourished infants in the 2nd to 6th months of life, in adults with malignant disease, particularly after treatment with cytotoxic agents, after transplantation and immunosuppresion and it is one of the most frequent causes of death in patients with AIDS. Inflammation causes a diffuse or patchy pneumonia and grossly, organ appears airless, red-violet, and beefy. Microscopically, the lesion comprises the thickened interstitium of interalveolar septa containing inflammatory infiltrate of lymphocytes, macrophages, and mainly plasma cells, diffuse alveolar damage and hyperplasia of type II pneumocytes. The alveolar spaces are filled with a characteristic eosinophilic or amphophilic, foamy, amorphous material, composed of proliferating parasites and cell debris. The organisms appear as small ”bubbles” in a background of proteinaceous exudate. 140. CYSTIC FIBROSIS OF THE PANCREAS (Mucoviscidosis) Cystic fibrosis is an autosomal recessive disorder occuring in children, which is characterized by defect in the secretory process of all exocrine glands affecting both mucussecreting and eccrine sweat glands throughout the body. The disease results from abnormal epithelial chloride transport. Clinical manifestations include chronic pulmonary disease, deficient exocrine pancreatic function, and other complications of inspissated thick mucus in a number of organs, including the small intestine, the liver and the reproductive tract. The pancreas becomes small, firm, grayish white, and on the cross section, it loses its characteristic triangular shape. In the late stages, there are numerous small cysts and the surface is granular. The large majority of patients have a form of chronic pancreatitis, which leads to loss of acinar cells and extensive fibrosis. Microscopically, both the ducts and acini are widely dilated and cystic and lined by atrophic flat cells.The lumina are distended with dense laminated or homogenous secretion. Squamous metaplasia of the ductal lining epithelium may be found in some cases as a result of impaired fat absorption including vitamin A. Dense fibrous tissue has formed around the lobule and between the persistent individual glands. On the contrary, the islets of Langerhans in this cystic fibrous tissue do not show marks of injury. In addition, there is scanty infiltration of lymphocytes and plasma cells. 119