Lymphoma describes cancer involving a specialized white blood cell called a lymphocyte. The cancerous lymphocytes multiply uncontrollably and take over any tissue they invade. Dogs with lymphoma have a range of symptoms: some may be asymptomatic (cancer found incidentally on examination), while others are quite ill. Diagnosis of lymphoma requires demonstration of cancerous lymphocytes within lymph nodes (either through an aspirate or biopsy sample) or other organs: spleen, liver, intestines, and bone marrow. Prior to treatment, your pet will have blood work done and be staged (e.g.: chest x-rays, abdominal ultrasound, and bone marrow evaluation) to determine the extent of the cancer and prognosis. Lymphoma is the most common (~90%) form of cancer associated with the blood cells. Fortunately, it is also tends to be the most responsive to chemotherapy treatment. Your veterinarian will discuss with you chemotherapy options and what to expect with treatment. Prognosis for lymphoma depends on 1) the stage of lymphoma that your pet has, 2) whether your pet is sick at the time of diagnosis or not, 3) response to chemotherapy, and 3) in cats, feline leukemia (FeLV) status.