November is National Pet Cancer Awareness Month. Last spring I wrote about canine lymphoma, so in honor of Cancer Awareness Month, I thought I would do the same for feline lymphoma.

What is Lymphoma?

Lymphoma is cancer of the immune system. The immune system is distributed throughout the body to protect against infections. Lymphoma in cats most commonly affects the gastrointestinal tract, although since the immune system is distributed throughout the body, lymphoma can be seen in any organ in the body including the eyes, in front of the heart, and in the kidneys, liver or spleen. Unlike canine lymphoma, feline lymphoma rarely occurs in the lymph nodes.

In cats (and also humans) it is not a single disease, but is probably more than 20 different diseases; each of the 20 or so forms of lymphoma behaves somewhat differently and the prognosis varies between types. The most common form of lymphoma we see in cat intestines is called small cell lymphoma. We also see an intestinal variant called large cell lymphoma. The photomicrograph on the right shows a rare form of feline lymphoma called large granular lymphoma. The name comes from the granules seen in some of the cancerous lymphocytes.

How is Lymphoma Treated?

Three major types of treatments underlie all cancer therapy: surgery, radiation therapy and chemotherapy. Since lymphoma is widespread throughout the body at the time of diagnosis, surgery is not generally used for treatment as removal of all the lymph tissue in the body is impossible, but sometimes a solitary mass of lymphoma may be removed from the intestine if the mass is causing problems for the cat. Surgery may also be recommended to obtain a biopsy for diagnosis. Radiation therapy can be used in select cases of feline lymphoma, especially if chemotherapy stops working. However, chemotherapy remains the mainstay of feline lymphoma treatment.

Multiple Lymphoma Protocols

In my office file drawers, I have a big fat folder of articles describing various chemotherapy protocols for the treatment of lymphoma. Many of them are simply a riff on a theme. In my opinion, there are three basic options for chemotherapy of feline lymphoma:

1. Steroids, glucocorticoids, cortisone, and prednisone are all names for the same type of drug. In lymphoma, steroids kill the cancer cells but are not “traditional” chemotherapy agents.
2. Treatment with a single chemotherapy drug. This is most commonly used in intestinal small cell lymphoma. Steroids and chlorambucil can keep a cat with small cell lymphoma in remission for months.
3. Using multiple chemotherapy drugs known to be effective against lymphoma and combining them into a rotational schedule which minimizes toxicity and maximizes efficacy.

How Long Will My Cat with Lymphoma Live?

Like with dogs, the answer is: it depends. Cats treated for small cell intestinal lymphoma often live 2-3 years and some can even discontinue chemotherapy. More aggressive forms of lymphoma like large cell lymphoma may only survive months despite multi-agent chemotherapy. A board certified veterinary oncologist can give you the most accurate prognosis for your cat.

Helpful Hints About Lymphoma

• Feline lymphoma is an internal disease. Cat owners will notice weight loss, poor appetite and possibly vomiting/diarrhea which are common clinical signs of multiple cat illnesses like inflammatory bowel disease, pancreatitis and diabetes. A full medical evaluation is required to make a lymphoma diagnosis.
• Because cat lymphoma typically occurs in the intestines, biopsies are frequently used to diagnose lymphoma in cats. Often high tech testing like flow cytometry or DNA analysis are required to confirm a lymphoma diagnosis in a cat.
• In a survey of cat owners who chose to treat their cat’s lymphoma, 85% were completely satisfied with their decision.