What is the recommended diagnostic approach for suspected small intestinal T-cell lymphoma in cats?

• A. Full-thickness biopsy
• B. Endoscopy with only mucosal biopsy
• C. Fine-needle aspiration
• D. Serosal biopsy

Answer: (A)

When suspected small intestine T-cell lymphoma in a cat, you need tissue that shows all layers of the bowel wall. The malignant cells often spread through deeper layers (submucosa and beyond), not just the mucosa. A full-thickness biopsy provides samples from mucosa, submucosa, muscularis, and serosa, giving pathologists the architectural context needed to confirm lymphoma, assess depth of invasion, and apply immunohistochemistry to identify the T-cell phenotype. This makes it the most reliable way to establish the diagnosis and guide treatment.

Endoscopic sampling of only the mucosa may miss submucosal disease and can yield nondiagnostic results because the infiltrate is not confined to the surface. Fine-needle aspiration collects cells without preserving tissue architecture, which limits definitive lymphoma diagnosis and staging. Serosal biopsy samples only the outer layer and misses the disease that typically lies within the mucosa and submucosa. Therefore, obtaining a full-thickness biopsy, usually surgically or laparoscopically, offers the highest diagnostic yield for this condition.