Feline Gastrointestinal Lymphoma Study Guide

Overview and Clinical Importance

Gastrointestinal (GI) lymphoma is the most common neoplasm in cats, accounting for 50-70% of all feline lymphoma cases and approximately 30% of all feline cancer diagnoses. Following the decline of feline leukemia virus (FeLV) due to widespread vaccination, the alimentary form has become the predominant anatomical location. GI lymphoma is classified into two distinct clinical entities based on lymphocyte size: low-grade alimentary lymphoma (LGAL), also known as small cell lymphoma, and high-grade alimentary lymphoma (HGAL), also known as large cell or intermediate-to-high-grade lymphoma. This distinction is critical for the NAVLE as it directly impacts treatment selection and prognosis.

Epidemiology and Risk Factors

GI lymphoma predominantly affects middle-aged to older cats with a median age of 10-13 years at diagnosis. There is no consistent breed or sex predisposition, though domestic shorthair cats are most commonly affected due to population prevalence. Unlike mediastinal or multicentric forms, alimentary lymphoma has the weakest association with FeLV antigenemia. Environmental factors, particularly secondhand tobacco smoke exposure, have been associated with a doubled risk of developing lymphoma in cats.

Classification of Feline GI Lymphoma

Clinical Presentation

Small Cell Lymphoma (LGAL)

Cats with LGAL typically present with chronic, insidious clinical signs that have been present for weeks to months (median 6 months). Signs may intermittently respond to supportive medications such as antiemetics or dietary changes. Common presentations include weight loss (most consistent finding), chronic vomiting, diarrhea (small bowel or mixed), decreased or increased appetite, and lethargy. Physical examination may reveal a thin body condition score, palpably thickened intestinal loops described as having a "ropey" sensation, or may be entirely unremarkable.