Canine and Feline Lymphoma - Similar But Not Identical Diseases

By Jennifer Coates, DVM on Aug. 7, 2012

Lymphoma is one of the most common types of cancer that I diagnose in cats and dogs. We’ve talked before about a potential breakthrough in the treatment of this disease in dogs, but haven’t really touched upon the nuts and bolts of the disease and its treatment in either species. Let me set that right today.

Lymphoma (or lymphosarcoma, as it is also called) results from the unregulated growth of malignant lymphocytes (a type of white blood cell). In dogs, the disease typically affects lymph nodes (most obviously observed in the chest region, armpits, behind the knees, groin, and/or under the jaw), bone marrow, liver, and spleen, but can also be seen in the eyes, skin, and gastrointestinal tract. In cats, the chest, kidneys, nose, skin, spine, and gastrointestinal tract are the most commonly involved parts of the body.

Many dogs present with enlarged lymph nodes and no other clinical signs of illness, while some dogs and most cats have symptoms such as depression, lethargy, vomiting, weight loss, decreased appetite, hair loss, and fever. Lymphoma can usually be diagnosed with routine lab work and an aspirate or biopsy of the affected tissues, although more specialized tests are sometimes necessary to reach a definitive diagnosis. There are several classification systems for lymphoma based on whether it is high, intermediate, or low grade (a measure of aggressiveness), where it is located in the body, and what type of cells are involved (T- or B- lymphocytes).

Chemotherapy is the treatment of choice for most pets with lymphoma. Surgery may be an option when the disease in confined to a specific part of the body. There are a wide range of chemotherapeutic drugs that can be used to treat this disease, and they generally work best when given in combination. Using the steroid prednisone alone can improve the quality, and sometimes quantity of life. While there is no cure for lymphoma in dogs and cats, chemotherapy often results in remission (no outward signs of cancer).

In dogs, the first remission can last 6 to 8 months or more depending on the chemotherapy protocol used. A second remission is generally a little more difficult to achieve and lasts a shorter time. Survival times average between 9 and 12 months but can be significantly shorter or longer in certain cases. Prognosis is better if an animal presents with only enlarged lymph nodes and with B-cell lymphoma rather than T-cell lymphoma. A dog appropriately treated for lymphoma can live a comfortable, happy life for many months.

Unfortunately, the prognosis is not as good for cats as it is for dogs. About 75 percent of cats go into remission with treatment, but the median survival time is usually only 6 months. If left untreated, most cats will not survive longer than 4-6 weeks after diagnosis. Palliative care like nutritional therapy and pain medication can help keep cats comfortable as the disease progresses.

A personalized treatment plan is important to slow the progression of lymphoma. Talk to your veterinarian about what is best for your pet.