Definitive diagnosis of suspected intestinal small cell lymphoma in cats typically requires which type of biopsy?

• A. Endoscopic mucosal biopsy only
• B. Serosal biopsy
• C. Fine-needle aspiration of the mucosa
• D. Full-thickness intestinal biopsy

Answer: (D)

For a definitive diagnosis of intestinal small cell lymphoma in cats, you need tissue that preserves the full structure of the intestinal wall. The lymphoma often involves deeper layers—mucosa and submucosa—and the pattern of infiltration, along with the ability to perform immunohistochemistry and clonality testing, is essential to distinguish it from inflammatory disease. Endoscopic biopsies that sample only the mucosa may miss submucosal involvement and often don’t provide enough tissue for accurate histopathology or ancillary tests. Serosal tissue isn’t representative of the primary disease and isn’t helpful for this diagnosis. Fine-needle aspiration of the mucosa yields cells without the architectural context needed to differentiate neoplastic from reactive lymphoid tissue. A full-thickness intestinal biopsy provides tissue from all layers, allowing proper assessment of infiltration depth and architecture and enabling definitive diagnostic testing.