Feline gastrointestinal lymphoma.

Gastrointestinal lymphoma is a common cause of anorexia and weight loss in older cats, with or without vomiting or diarrhea. Most cats are feline leukemia virus-negative and feline immunodeficiency virus-negative. Low-grade gastrointestinal lymphoma may be more common than previously thought, and these cats respond better to chemotherapy agents than cats with high-grade lymphoma. The most significant prognostic indicator is initial response to chemotherapy, with cats that survive the initial induction period generally achieving long-term remission. Thus far, investigations into molecular markers and immunophenotyping have failed to identify useful prognostic indicators.