Principles of treatment for feline lymphoma.

Lymphoma is the most commonly diagnosed neoplasm in cats. As feline leukemia virus antigenemia has decreased over the past 15 years, there has been a profound shift in the presence, signalment, and frequency of sites of feline lymphoma in North America. There is variation in anatomic classification systems, but most studies have divided lymphoma into four groups: alimentary, mediastinal, multicentric, or extranodal. Clinical signs and common differential diagnoses for each of the forms are described. Staging allows for evaluation of the extent of disease. As in the dog, lymphoma is a systemic disease in the cat, and chemotherapy is the treatment of choice for most forms. Exceptions are described. In contrast to canine lymphoma, feline lymphoma is generally more challenging and frustrating to treat than canine lymphoma. Response rates are lower, and remission duration is shorter. Fortunately, cats treated with chemotherapy tend to have less toxicity than dogs. Positive prognostic factors are feline leukemia virus-negative, clinically well at time of diagnosis, and response to therapy. Achieving a complete remission is prognostic for survival. Unfortunately, response cannot be predicted before treatment.