1. Neoplasia

University of Kufa
Faculty of Veterinary Medicine
Third year
Dr. Hutheyfa Al Salih
Neoplasia is the uncontrolled, disorderly proliferation of cells, resulting in a benign or
Malignant growth known as a neoplasm (in ancient Greek, neo = new and plasma = creation).
In common medical usage, a neoplasm often is referred to as a tumor, and the study of
tumors is called oncology (from oncos, “tumor,” and logos, “study of”). the division of
neoplasms into benign and malignant categories.
All tumors have two basic components:
(1) Neoplastic cells that constitute the tumor parenchyma
(2) Reactive stroma made up of connective tissue, blood vessels, and variable numbers of
cells of the adaptive and innate immune system.
The classification of tumors and their biologic behavior are based primarily on the
parenchymal component, but their growth and spread are critically dependent on
their stroma.
Benign tumor
Benign tumor is microscopic and gross characteristics are considered, relatively innocent
implying that it will remain localized and is amenable to local surgical removal.
In general, benign tumors are designated by attaching the suffix -oma to the name of the
cell type from which the tumor originates.
Tumors of mesenchymal cells generally follow this rule. For example, a benign tumor
arising in fibrous tissue is called a fibroma, whereas a benign cartilaginous tumor is a
The nomenclature of benign epithelial tumors is more complex; some are classified based
on their cells of origin, others on microscopic pattern, and still others on their macroscopic
 Adenoma is applied to benign epithelial neoplasms derived from glands, although they
may or may not form glandular structures.
 Benign epithelial neoplasms producing microscopically or macroscopically visible
fingerlike or warty projections from epithelial surfaces are referred to as papillomas.
 Those that form large cystic masses, such as in the ovary, are referred to as
 When a neoplasm benign or malignant produces a macroscopically visible projection
above a mucosal surface and projects, for example, into the gastric or colonic lumen,
it is termed a polyp.
Malignant Tumors
Malignant tumors are collectively referred to as cancers. Malignant tumors can invade and
destroy adjacent structures and spread to distant sites (metastasize) to cause death.
The nomenclature of malignant tumors essentially follows the same schema used for
benign neoplasms, with certain additions.
Malignant tumors arising in solid mesenchymal tissues are usually called sarcomas (Greek
Those arising from blood-forming cells are designated leukemia (literally, white blood) or
lymphomas (tumors of lymphocytes or their precursors).
Malignant neoplasms of epithelial cell origin, derived from any of the three germ layers,
are called carcinomas. Thus, cancers arising in the ectodermally derived epidermis, the
esodermally derived renal tubules, and the endodermally derived lining of the
gastrointestinal tract are all termed carcinomas.
Carcinomas may be further qualified. Squamous cell carcinoma denotes a cancer in which
the tumor cells resemble stratified squamous epithelium, and adenocarcinoma denotes a
lesion in which the neoplastic epithelial cells grow in a glandular pattern.
Sometimes the tissue or organ of origin can be identified and is added as a descriptor, as in
renal cell adenocarcinoma or bronchogenic squamous cell carcinoma.
Characteristics of benign and malignant neoplasms
I. Differentiation and Anaplasia
Differentiation refers to the extent to which neoplasms resemble their parenchymal cells of
origin, both morphologically and functionally; lack of differentiation is called anaplasia.
Benign neoplasms are composed of well-differentiated cells that closely resemble their
normal counterparts.
By contrast, while malignant neoplasms exhibit a wide range of parenchymal cell
differentiation, most exhibit morphologic changes that resemble their malignant nature.
Tumors composed of undifferentiated cells are said to be anaplastic, a feature that is a
reliable indicator of malignancy.
Anaplastic cells morphologic features:
1. Pleomorphism
Variation in size and shape). Thus, cells within the same tumor are not uniform, but range
from small cells with an undifferentiated appearance, to tumor giant cells many times larger
than their neighbors.
2. Nuclear abnormalities
Consisting of extreme hyper-chromatism (dark-staining), variation in nuclear size and
shape, or unusually prominent single or multiple nucleoli. Enlargement of nuclei may result
in an increased nuclear-to-cytoplasmic ratio.
3. Tumor giant cells formation
These are considerably larger than neighboring cells and may possess either one enormous
nucleus or several nuclei.
4. Atypical mitoses
Mitosis may be numerous. Anarchic multiple spindles may produce tripolar or quadripolar
mitotic figures.
5. Loss of polarity
Anaplastic cells lack recognizable patterns of orientation to one another. Such cells may
grow in sheets, with total loss of communal structures, such as glands or stratified
squamous architecture.
II. Rate of growth
Most benign tumors grow slowly, and most cancers grow much faster, eventually spreading
locally and to distant sites (metastasizing) and causing death.
The rate of growth of malignant tumors usually correlates inversely with their level of
differentiation. In other words, poorly differentiated tumors tend to grow more rapidly than
do well-differentiated tumors.
III. Local invasion
The growth of malignant tumors is accompanied by progressive infiltration, invasion,
and destruction of the surrounding tissue,
Nearly all benign tumors grow as cohesive expansile masses that remain localized to
their site of origin and lack the capacity to infiltrate, invade, or metastasize to distant
Because benign tumors grow and expand slowly, they usually develop a rim of
compressed fibrous tissue called a capsule that separates them from the host tissue.
IV. Metastasis
Metastasis is defined by the spread of a tumor to sites that are physically discontinuous
with the primary tumor, and unequivocally marks a tumor as malignant, as by definition
benign neoplasms do not metastasize.
The invasiveness of cancers permits them to penetrate into blood vessels, lymphatics, and
body cavities, providing the opportunity for spread. All malignant tumors can metastasize,
but some do so very infrequently.
The development of metastases, invasiveness is the feature that most reliably distinguishes
cancers from benign tumors.
Pathways of spread
1. Seeding of body cavities and surfaces
Seeding of body cavities and surfaces may occur whenever a malignant neoplasm
penetrates into a natural “open field” lacking physical barriers. Most often involved
is the peritoneal cavity, but any other cavity pleural, pericardial, subarachnoid, and joint
spaces may be affected.
2. Lymphatic Spread
Transport through lymphatics is the most common pathway for the initial dissemination
of carcinomas
Sentinel lymph node is the first regional lymph node that receives lymph flow from a
primary tumor. It can be identified by injection of blue dyes or radiolabeled tracers near
the primary tumor. Biopsy of sentinel lymph nodes allows determination of the extent of
spread of tumor.
3. Hematogenous Spread
Hematogenous spread is typical of sarcomas but is also seen with carcinomas. Arteries,
their thicker walls, are less readily penetrated than are veins.
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