Lymphoma in Cats ~ Pawprints and Purrs, Inc.

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Lymphoma in Cats

Cats have a higher incidence of lymphoma than dogs or people. Feline Lymphoma is much more common in cats who are infected with feline leukemia virus (FeLV). Lymphoma is a rapidly growing malignancy that is able to go and grow anywhere where there is lymph tissue, which is virtually every organ in the body. Eventually, the cancer will infiltrate an organ to such an extent that it fails (often this is the bone marrow or the liver). The patient loses his/her appetite, vomits or gets diarrhea, weakens, and dies. At some point the tumor becomes resistant to therapy and no further remissions can be obtained. Feline Lymphoma is usually treated with chemotherapy which, depending on the location and form, can be very successful with high remission rates and a significantly increased life span.

Which cats are at risk for developing feline lymphoma?

There is no breed or sex predilection for cats who develop Feline Lymphoma. In the past, the average age of cats diagnosed with lymphoma was about 5 years. More recently, the average age has steadily risen to 9 - 10 years. The reason for the increase in age is that more cats are being tested and vaccinated for Feline Leukemia and have limited exposure to potentially infected cats. As a result, the incidence of feline leukemia (and thus lymphoma) in young cats has decreased. Cats who are not infected with FeLV generally develop lymphoma when they are much older. Thus the average age of affected cats is increasing.

As mentioned, lymphoma has traditionally been correlated with infection with FeLV. In the past, some studies found that up to 70% of all cats that developed feline lymphoma tested positive for FeLV. Some of the most recent studies show that number to be dropping and FeLV positive cats may now account for only 20% of the new cases. Cats infected with feline Immunodeficiency Virus (FIV) are also at greater risk of developing Feline Lymphoma. Now that the virus has become less common, thanks to more cats living indoors, effective vaccination, and readily available testing procedures, causes of lymphoma are more obscure. Cigarette smoke in the home has been found to double a cat's risk though genetic issues; environmental chemicals and unknown factors remain under consideration. Lymphoma can occur anywhere in the body where there is lymph tissue.

Are there different forms of feline lymphoma?

Feline lymphoma has several different forms. In all forms, the tumors consist of abnormal proliferations of lymphoid tissue. Because lymphocytes and lymph tissue are found throughout the body, lymphoma can appear almost anywhere and affect a wide number of organs. Lymphoma more commonly appears, though, in three parts of the body. The location is often associated with the cause of the lymphoma and influences the symptoms, treatment, and prognosis.

The multicentric form generally involves multiple lymph nodes and possibly multiple organs. This form is more closely associated with feline leukemia and the prognosis for this form is not as good, especially if the cat is feline leukemia positive.

The mediastinal form is also associated with feline leukemia. This form is found in the chest cavity and will affect the thymus and associated lymph nodes.

The alimentary form affects the digestive tract and surrounding lymph nodes. This form is least likely to be associated with feline leukemia.

In all forms, the treatment outcome is more guarded if the cat is positive for feline leukemia.

What are the symptoms of lymphoma in cats?

Cats who develop lymphoma are much more likely to develop more severe symptoms than dogs. Dogs often appear healthy except for swollen lymph nodes; cats will often be physically ill. The symptoms correspond closely to the location of the lymphoma. Cats with the alimentary form of lymphoma often present with weight loss, rough hair coat, loss of appetite, vomiting and diarrhea. Cats with the mediastinal form often have respiratory distress and fluid in the lung cavity. If lymphoma develops in the kidney, the cat may have increased water consumption and increased urination. If the lymphoma is located in the nose, the cat may have discharge from the nose and facial swelling. Cats who are also infected with FeLV often present with pale mucous membranes due to anemia.

How is feline lymphoma diagnosed?

Diagnosis of lymphoma in cats is based on a series of observations and tests. A physical exam may revealing swellings in the lymph nodes or GI tract. X-rays, ultrasounds, or physical examinations may show tumors or swellings in other internal organs. Testing for FeLV and FIV may reveal that a cat is positive for one of these diseases, which increases the likelihood that he could develop feline lymphoma. A chemistry panel and complete blood count (CBC) may reveal particular organ involvement or an anemia, particularly in the multicentric form or in the FeLV positive cat. Fine needle aspirate or biopsies are often diagnostic for feline lymphoma. When a trained pathologist examines a fine needle aspirate or a biopsy, he or she is looking for a uniform population of immature lymphoid cells, which confirms feline lymphoma.

How is feline lymphoma treated?

Treatment for feline lymphoma usually consists of chemotherapy. In a few isolated cases where the tumor is localized and easily accessible, surgery or radiation therapy may be used. The chemotherapy protocol for cats is similar to that in dogs with a few minor changes in drug combinations. A combination of chemotherapy drugs including doxorubicin, cyclophosphamide, vincristine, and prednisone administered over many weeks is the most common course of treatment. During the course of treatment white and red blood cell numbers are closely monitored. Individual treatment programs differ from veterinarian to veterinarian.

What is the prognosis for a cat with lymphoma?

The remission and survival rates of cats with lymphoma vary depending on the cat's FeLV status, the location of the tumor(s) and how quickly the tumor is diagnosed and treated. In general, about 70% of cats will respond to the chemotherapy treatment. On average, these cats will live an additional 4 to 6 months. However, about 30% - 40% of the cats that respond will go into a more complete remission that can last for 2 years or longer. This potential response is encouraging and is the reason that treatment for lymphoma in cats is so highly recommended. Cats who are not treated have an average survival time of only 4 to 6 weeks once the diagnosis has been made. Cats who are infected with FeLV or FIV have a lower rate of response to therapy as well as a shorter average survival time when treated. It is best to focus on a realistic outcome, which is the longest possible survival with good quality life.

Conclusion

Feline lymphoma is a fairly common cancer of cats. In the past it was closely linked to infection with FeLV but, with a decrease in the incidence of feline leukemia, more cats with lymphoma are FeLV negative. Feline lymphoma can strike a variety of different organs but always involves a proliferation of lymphoid cells. About 70% of infected cats respond favorably to chemotherapy treatment and a fair number can see an increased life span of two years or more. Because of the close link to infection with FeLV and FIV, one of the best things guardians can do to reduce the risk of their cats developing lymphoma is to protect them against infection with FeLV and FIV. Eliminating exposure to other cats is the best preventative. If your cat is exposed to other cats (e.g.; goes outside, to cat shows, etc.) consider FeLV vaccination.

Additional Information:

Cancer & Chemotheraphy in Companion Animals
Feline Lymphoma Caregivers Guide
Feline Lymphoma Leahy Animal Hospital, PC
Feline Lymphoma Mar Vista Animal Medical Center
Lymphoma in the Cat

Page URL: http://www.sniksnak.com/cathealth/lymphoma.html

Resource References:
Much, much appreciation to Dr. Raymond Van Lienden, DVM of Clifton, VA USA for his extensive research in locating the material found on this page. Thank you, dear Doctor!