NAVLE Veterinary Pathology and Necropsy Interpretation

Question 1

Necropsy of an 8-year-old dog reveals a 4 cm hepatic mass with a tan cut surface, no central necrosis, and a pushing border compressing but not invading adjacent parenchyma. Histology shows well-differentiated hepatocytes in a solid pattern. The most appropriate classification is:

Accepted Answer

Hepatocellular adenoma (hepatoma) — typically benign, wide surgical excision curative

Answer

Hepatocellular adenomas (hepatomas) are well-encapsulated, well-differentiated benign tumors in dogs with a pushing border and no invasion. Hepatocellular carcinoma shows vascular invasion, necrosis, and nuclear pleomorphism. Nodular hyperplasia is typically multifocal and small (≤1 cm). Metastatic carcinoma would show an infiltrative pattern and non-hepatocyte histology.

Question 2

A 6-month-old calf dies acutely. Necropsy reveals a 'paint-brush' hemorrhage pattern on the epicardium, fibrinonecrotic plaques in the abomasum, and hemorrhagic lymph nodes. Which pathologic process most likely caused these lesions?

Accepted Answer

Septicemia with gram-negative lipopolysaccharide-mediated disseminated intravascular coagulation (DIC)

Answer

Petechial/ecchymotic hemorrhages (paint-brush pattern) on serosal surfaces combined with hemorrhagic lymph nodes and mucosal necrosis are classic findings of endotoxemia-induced DIC in calves, most commonly from gram-negative septicemia (e.g., Salmonella, E. coli). LPS activates the coagulation cascade, consuming clotting factors and causing bleeding diathesis. White muscle disease shows pale streaking of skeletal/cardiac muscle.

Question 3

Histologic examination of a canine skin biopsy shows epidermal hyperplasia, parakeratosis, Munro microabscesses (neutrophil collections in the stratum corneum), and perivascular lymphocytic infiltrate in the superficial dermis. This pattern is most consistent with:

Accepted Answer

Psoriasiform-lichenoid dermatitis

Answer

Psoriasiform-lichenoid dermatitis in dogs is characterized histologically by epidermal hyperplasia (psoriasiform), parakeratosis, intracorneal neutrophil accumulations (Munro microabscesses), and a lichenoid (interface) or superficial perivascular infiltrate. Pemphigus foliaceus shows acantholytic cells and subcorneal pustules; pyoderma shows suppurative folliculitis.

Question 4

A 10-year-old cat dies of renal failure. Necropsy shows bilaterally small, pale, irregularly pitted kidneys. Histology reveals tubular atrophy, interstitial fibrosis, glomerulosclerosis, and lymphoplasmacytic interstitial infiltrate. The most accurate pathologic diagnosis is:

Accepted Answer

Chronic tubulointerstitial nephritis (end-stage kidney disease)

Answer

Chronic tubulointerstitial nephritis is the most common cause of chronic kidney disease (CKD) in cats. The classic gross appearance is bilaterally symmetrical small, pale, granular kidneys. Histologically the hallmark is tubular atrophy, interstitial fibrosis, and lymphoplasmacytic infiltrate — representing end-stage scarring. Acute tubular necrosis shows tubular swelling and necrosis without fibrosis. FIP nephritis is pyogranulomatous with vasculitis.

Question 5

Cytology of a fine-needle aspirate from a splenic mass in a 9-year-old Golden Retriever shows large cells with abundant cytoplasm containing hemosiderin, erythrophagocytosis, and rare mitotic figures with no distinct cell clusters. The most appropriate interpretation is:

Accepted Answer

Histiocytic sarcoma — aggressive malignancy requiring staging

Answer

Large pleomorphic cells with erythrophagocytosis and abundant cytoplasm on splenic aspirates are characteristic of histiocytic sarcoma, an aggressive malignancy particularly prevalent in Golden Retrievers and Bernese Mountain Dogs. Hemangiosarcoma is notoriously poorly exfoliating on FNA (blood only usually). Lymphoma shows small-to-large lymphocytes. Extramedullary hematopoiesis lacks pleomorphic large macrophagic cells.

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE Veterinary Pathology and Necropsy Interpretation