Case # 1:
A one year old, female, domestic long hair, feline in slightly thin body condition
was submitted for post mortem examination. Approximately one week ago, this
animal began to have respiratory difficulty, became lethargic followed by an
inability to rise. Prior to euthanasia, physical examination revealed open mouth
breathing, muffled cranial lung sounds and caudal displacement of the heart
sounds. On palpation, the chest could not be compressed.
Courtesy of the AVC radiology dept.
Questions:
1. Describe the lesion.
2. What is the most likely underlying process?
a. Inflammation
b. Neoplasia
c. Hyperplasia
d. Degenerative
3. What is an appropriate morphological diagnosis?
a. Cranial mediastium/thymus; primary malignant neoplasia
4. What are some differential diagnoses for this lesion? And what
different cell populations do they arise from?
a. Mediastinal (thymic) lymphoma – lymphoid population
(Fry and McGavin 2007)
Please Note: the sheets of neoplastic round cells with scant
pale pink (eosinophilic) cytoplasm shown in the images above.
b. Thymoma – epithelial population
(Fry and McGavin 2007)
Please Note: the red arrow points to the neoplastic epithelial
cells while the green arrow points to the resident small
lymphocyte population (normal)
5. Given the young age of this cat and what you know about this
disease process in the feline, what is the mostly likely underlying
etiology/cause?
a. Feline lymphoma can be caused by horizontal transmission of
the Feline leukemia virus. Infected cats that develop
lymphoma are typically young and often develop the
mediastinal (thymic) or multicentric forms (mostly T-cell
lymphomas).
References:
Fry, M. M. and M. D. McGavin (2007). Bone marrow, blood cells and lymphatic system.
Pathologic Basis of Veterinary Disease. M. D. McGavin and J. F. Zachary.
Case # 2:
An 8 year old, female spayed, Cocker Spaniel is submitted for post mortem
examination. Prior to euthanasia, physical examination revealed enlargement of
the peripheral lymph nodes.
Questions:
1. Describe the lesion.
2. What is an appropriate morphological diagnosis?
a. Severe, diffuse splenomegaly
3. Which of the following terms best describes the texture of this
organ?
a. Meaty
b. Bloody
4. What are some differential diagnoses that could result in this lesion?
a. Hemolytic disease
b. Septicemia
c. Lymphoma
d. Mast cell neoplasia
e. Histioctyic sarcoma
f. Granulomatous disease (Histoplasmosis)
g. Amyloidosis
5. Many of these differential diagnoses share a common feature that
results in this lesion and altered organ texture. What is the most
likely common feature?
a. Proliferation of cells within the spleen
diffuse splenic
enlargement
Case #3:
An adult Holstein cow (between 6-7 years of age) is submitted for postmortem
examination. The cow was down and unable to rise. Antemortem physical
examination revealed multiple enlarged peripheral lymph nodes and protrusion of
her eye.
Questions:
1. Describe the lesion.
2. What is the most likely underlying process?
a. Inflammation
b. Neoplasia
c. Hyperplasia
d. Degenerative
3. What is an appropriate morphological diagnosis?
a. Multicentric lymphoma (abomasums, lymph nodes, heart,
spinal cord/meninges, vertebral bodies, kidney)
4. In the bovine, this disease falls into two main categories. Please list
these two categories and their 2 critical defining features (Hint: it
involves age and etiology).
a. Enzootic bovine lymphoma – adult cattle, Bovine Leukemia
Virus positive
b. Sporadic bovine lymphoma – young cattle, Bovine Leukemia
Virus negative
5. Given the age of this cow and the distribution of these lesions, which
category does this case best fit and what is the mostly likely
underlying etiology/cause?
a. Enzootic bovine lymphoma – this is typically a multicentric
disease of adult cattle (avg. age 5-8 years) and most commonly
affects the lymph nodes, heart (right atrium especially),
abomasums, uterus, vertebral canal, kidneys, and retro-orbital
space. The etiologic agent is Bovine Leukemia Virus (BLV), an
oncogenic retrovirus, that is transmitted via transfer of viralinfected lymphocytes; mostly horizontal by arthropods, natural
breeding and accidental transmission by repeatedly used
needles, ear tagging equipment, palpation gloves, etc. The
virus causes a lifelong infection and targets B-lymphocytes.
Approximately 30% infected animals develop a non-neoplastic
lymphocytosis while only a small percentage (<5%) develop
lymphoma.
Case # 4:
A spleen from a 10 year old, mixed breed, canine is submitted for histopathology.
Questions:
1. Describe the lesion.
2. Which of the following terms best describes the texture of these
masses?
a. Firm
b. Bloody and soft/fluctuant
3. What are some differential diagnoses for these “nodules”?
a. Nodular hyperplasia
b. Primary neoplasia
c. Metastatic neoplasia
d. Abscess
e. Granuloma
4. Assuming we are unsure as to the exact nature of these masses (ie.
benign versus malignant versus inflammatory), what would be an
appropriate morphological diagnosis?
a. Multifocal to coalescing splenic nodules or masses
5. Let’s say this dog is otherwise healthy, given the age of the animal
and the appearance of these “nodules”, what is your top differential
diagnosis?
a. Nodular hyperplasia – common incidental finding in aged dogs.
6. If a small, irregular to nodular mass were found within the right
auricle of the heart, what would be your next top differential
diagnosis for these splenic masses?
a. Hemangiosarcoma
Case # 5:
Abnormalities were detected within the carcass of a mature, beef cow following
slaughter.
Questions:
1. Describe the lesion.
2. What is the most likely underlying process?
a. Inflammation/Infectious
b. Neoplasia
c. Hyperplasia
d. Degenerative
3. What is an appropriate morphological diagnosis?
a. Lymph node; multifocal, nodular, chronic, granulomatous
lymphadenitis
(Note: in some cases, when describing granulomatous
inflammation the word chronic may be excluded as it is felt to
be redundant)
4. What etiologic agent would most likely cause these lesions?
a. Mycobacterium bovis
5. What is the common disease name?
a. Bovine tuberculosis
Case # 6:
An adult ewe with a recent history of submandibular and prescapular lymph node
enlargement was found dead in the field.
Questions:
1. Describe the lesion.
2. What is an appropriate morphological diagnosis?
a. Caudal mediastinum; Moderate, multifocal, chronic,
suppurative lymphadenitis
3. What is the common name for this condition?
a. Caseous lymphadenitis
4. What is the most likely infectious agent that would produce this type
of lesion?
a. Corynebacterium pseudotuberculosis
i. A small gram-positive rod and facultative intracellular
parasite that is found on fomites and in soil and
manure contaminated with purulent exudates
5. How can we explain location of these masses (hint: how and why did
the masses develop in the tissues shown here)?
a. Infection occurs after C. pseudotuberculosis penetrates
through unbroken or abraded skin or through mucous
membranes. The bacteria proliferate producing slowly
enlarging, localized, and non-painful abscess that typically
develop either at the point of entry (in the skin) or in the
regional lymph nodes (superficial or external form). From
there the bacteria spread via the blood or lymphatic system
and cause abscessation of internal lymph nodes or organs
(visceral or internal form).
6. Can you list some other agents that may cause similar lesions in
other species (including the horse, pig, and dog)?
a. Horse: Equine strangles – Streptococcus equi subsp. equi
b. Pig: Porcine jowl abscess – Streptococcus porcinus
c. Dog: Streptococcal adenitis – Streptococcus sp. (Lancefield’s
group G)