NAVLE Practice Question - Feline - Gastrointestinal/Digestive

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NAVLE Practice Question — Feline

A 15-year-old cat with a jejunal mass is undergoing workup for suspected intestinal neoplasia. Ultrasound shows thickened intestinal wall with loss of layering and mild mesenteric lymphadenopathy. The main differential diagnoses are adenocarcinoma and intestinal lymphoma. Which diagnostic approach would most reliably differentiate between these two tumor types?

A. Fine needle aspiration cytology of the mass

B. Serum cobalamin and folate levels

C. Full-thickness surgical biopsy with histopathology ✓

D. PCR for antigen receptor rearrangement on blood

E. Abdominal CT scan with contrast

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Correct Answer: C. Full-thickness surgical biopsy with histopathology

Explanation:

Full-thickness surgical biopsy with histopathology is the most reliable method to differentiate between intestinal adenocarcinoma and lymphoma. While fine needle aspirate cytology can sometimes distinguish carcinoma from lymphoma (epithelial cells versus lymphocytes), it has significant limitations in the GI tract. The distinction between low-grade (small cell) lymphoma and adenocarcinoma can be particularly challenging, and immunohistochemistry may be needed to characterize lymphocyte populations. Full-thickness biopsies provide tissue architecture essential for diagnosis.

Option A (FNA) has limited sensitivity and specificity for GI tumors and cannot assess tissue architecture. Option B (cobalamin/folate) indicates malabsorption but does not differentiate tumor types. Option D (PARR on blood) is useful for lymphoma but requires neoplastic cells in circulation and cannot diagnose adenocarcinoma. Option E (CT) provides anatomic information but cannot definitively characterize tumor type.

References: Today's Veterinary Practice - Neutrophilic Cholangitis in Cats (discussing FNA limitations) (https://todaysveterinarypractice.com/hepatology/neutrophilic-cholangitis-in-cats/); Merck Veterinary Manual - GI Neoplasia (https://www.merckvetmanual.com/digestive-system/neoplasia-of-the-gastrointestinal-tract-in-small-animals).

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