poorer prognosis than other types, especially those with hypercalcemia. Clinical stage and substage have some prognostic value, with poorer prognosis associated with Stage V disease, and with substage b (clinical illness at time of presentation). Lymphoma in cats Lymphoma is the most common malignancy diagnosed in cats. Lymphoma in young cats occurs most frequently following infection with feline leukemia virus (FeLV) or to a lesser degree feline immunodeficiency virus (FIV). These cats tend to have involvement of lymph nodes, spine, or mediastinum. Cats with FeLV are 62 times more likely to develop lymphoma, and cats with both FeLV and FIV are 77 times more likely. Younger cats tend to have T-cell lymphoma and older cats tend to have B-cell lymphoma. Older cats tend to have gastrointestinal lymphoma without FeLV infection, although tests more sensitive to low level FeLV infections and replication-defective FeLV have found that many of these cats have been previously exposed. The same forms of lymphoma that are found in dogs also occur in cats, but gastrointestinal is the most common type. Lymphoma of the kidney is the most common kidney tumor in cats, and lymphoma is also the most common heart tumor. Classification Gastrointestinal lymphoma is classified into low grade, intermediate grade, and high grade. Low grade types include lymphocytic and small cell lymphoma. High grade types include lymphoblastic, immunoblastic, and large cell lymphoma. Low grade lymphoma is only found in the small intestine, while high grade can commonly be found in the stomach. Symptoms Cats that develop lymphoma are much more likely to develop more severe symptoms than dogs. Whereas dogs often appear healthy initially except for swollen lymph nodes, cats will often be physically ill. The symptoms correspond closely to the location of the lymphoma. The most common sites for alimentary (gastrointestinal) lymphoma are, in decreasing frequency, the small intestine, the stomach, the junction of the ileum, cecum, and colon. Cats with the alimentary form of lymphoma often present with weight loss, rough hair coat, loss of appetite, vomiting and diarrhea, although vomiting and diarrhea are commonly absent as symptoms. The tumor can also cause life-threatening blockage of the intestine. Cats with the mediastinal form often have respiratory distress and fluid in the thoracic cavity. If lymphoma develops in the kidney, the cat may have increased water consumption and increased urination. Lymphoma of the kidney presents as bilateral kidney enlargement and failure. If the lymphoma