Lymphoma can present in countless different ways. This is largely a consequence of the fact that lymphoma (and leukaemia) in cats can affect many different organs. Most classification schemes for feline lymphoma reflect the anatomic distribution of the lesions although some pioneers have noted the importance of the appearance of the cancerous cells. In human haemato-oncology, there are over 40 different kinds of lymphoma and leukaemia that are recognised and there are moves afoot to try to sub-classify lymphoma in dogs in similar ways.
Above: Pebbles who was extremely unwell with lymphoma in the chest, here 4 weeks after initiation of chemotherapy
Early investigations in feline lymphoma have failed to show prognostic significance associated with the T-cell or B-cell sub-types, which is considered one of the primary determinants of outcome in human and canine lymphoma. Undoubtedly further investigations in the future will help us to predict treatment response more reliably.
Currently, the most frequently diagnosed form of feline lymphoma is the alimentary or intestinal form. Patients often present with a history of reduced appetite, intermittent vomiting and sometimes a palpable mass in the abdomen. Diagnosis is made on biopsy, either by fine needle aspirate, core biopsy or surgical biopsy. In the absence of a detectable mass, some cases are presented with a generalised thickening of the intestine. These patients can have a much more insidious disease progression and may represent a different sub-type of feline lymphoma, often with a much improved prognosis.
Other frequent or notable lymphoma presentations include cranial mediastinal lymphoma and renal (kidney) lymphoma. For an unknown reason cranial mediastinal lymphoma is recognised more frequently in young cats, often only one year old. Cats will present to their veterinary surgeon with severe respiratory distress and chest x-rays indicate the presence of free fluid in the pleural space. A diagnosis can often be made on cytological analysis of the pleural fluid. These patients can be extraordinarily responsive to chemotherapy provided that the initial respiratory complaint can be stabilised.
Renal lymphoma appears to be a disease of the older cat. Cases usually present with reduced appetite and weight loss. Often an owner identifies a large intra-abdominal mass that is actually the enlarged left kidney. These cases invariably present with a degree of renal failure. Diagnosis is best made on a fine needle aspirate of an enlarged kidney. While they can be responsive to chemotherapy, the significant kidney damage that has inevitably arisen prior to diagnosis persists. This has consequences both in the short and the long term. In the short term, chemotherapy drug metabolism will inevitably be affected by the reduction in renal function. In the long term, renal damage is likely to be progressive and therefore, even if the lymphoma enters complete remission, life expectancy can be reduced.