Pet Columns, Office of Public Engagement, College of Veterinary Medicine at the University of Illinois at Urbana-Champaign

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Feline Lymphoma Can Go All Over

Pet Column for the week of September 21, 2009

Related information:

Related site - Veterinary Cancer Society

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Ashley Mitek
Information Specialist

Source - Laura D. Garrett, DVM, DACVIM
The number one cause of death in companion animals in this country is cancer. In our feline friends a specific type of cancer, lymphoma, is very common. The disease originates in the lymphocytes (white blood cells) of the immune system and frequently invades the lymph nodes causing them to enlarge.

Dr. Laura Garrett is a veterinary oncologist at the University of Illinois College of Veterinary Medicine in Urbana. She says, "lymphoma is common in middle-aged to older cats." Although it usually starts in tissues associated with the immune system (lymph nodes, liver, spleen, and bone marrow), it can set up shop in almost any part of the body because it has basically hijacked the blood supply.

Today, the most common form of lymphoma in cats is the gastro-intestinal variety. Patients present with symptoms such as weight loss, a loss of appetite, lethargy, vomiting, and diarrhea. However, years ago there was a different kind of lymphoma that predominated.

Multicentric (lymph node invasion) and mediastinal (a structure in the chest) forms used to be the most common. But as less and less cats become infected with the feline leukemia virus, these forms of the disease are less common. "If a young cat is diagnosed with lymphoma it is usually FeLV [feline leukemia virus] positive," explains Dr. Garrett.

This virus is directly linked to most forms of lymphoma, except the gastro-intestinal type that is now most prevalent. A cat infected with FeLV is 77 times more likely to develop lymphoma, and researchers have now shown that the virus can cause certain cells in the body to turn into malignant varieties.

A different type of virus that many cat owners have heard of, feline immunodeficiency virus (FIV), or more commonly known as "feline AIDS," can also increase the risk of lymphoma developing in infected cats. The current estimate is that FIV infected cats are five times more likely to develop lymphoma than those who test negative. Cats that are exposed to second-hand smoke are also at an increased risk.

If a veterinarian suspects lymphoma in a feline patient, it can be simple to diagnose. A fine needle aspirate, which is a minimally-invasive procedure, is performed by inserting a small gauge needle into an intestinal mass. After the sample is viewed under a microscope, if it contains a large percentage of lymphocytes, it is diagnosed as lymphoma.

Because lymphoma is a type of cancer that is termed "systemic," or infecting many different parts of the body, chemotherapy is necessary to treat. Because each patient is different and each form of lymphoma responds differently to the drugs, it's hard to put an exact number on what percentage of animals will go into remission. That said, in general, lymphoma responds well to such systemic therapy.

It is important to note that because veterinary medicine uses lower dosages of chemotherapy than human medicine, the majority of patients receiving treatment maintain a good quality of life. In addition, because a cat's hair does not continually grow like humans, they usually do not lose their fur coat during treatment.

For information regarding lymphoma, contact your local veterinarian. A list of board certified veterinary oncologists in your state can be found by visiting the Veterinary Cancer Society's Web site.