Feline Lymphoma: Causes

Feline lymphoma is one of the most common forms of cancer in cats and presents in many differentFeline Lymphoma: Causes forms, but all involve a common cell type from a lymphocyte, which is a type of white blood cell.  These cells are typically found in lymphoid tissues, such as lymph nodes, spleen and bone marrow.  However, lymphoma can develop from almost any tissue in the body.  The behavior of lymphoma in cats can vary depending on the location of the cancer in the cat and the grade of the tumor.  The grade of the tumor is broadly grouped into two categories, low grade and high grade.  The difference between these two grades is based in large part to the size of the cancer cells.  In low-grade lymphoma, the cells are of a small size, often referred to as small cell lymphoma.  In high-grade lymphoma, the cancer cells are large in size, often referred to as large cell lymphoma.

Causes of Feline Lymphoma

The feline leukemia virus  (FeLV) is the most common known cause of lymphoma in cats.  This wasFeline Leukemia Vaccine particularly the case in the 1960s-1980s when 60-70% of lymphoma in cats was due to the FeLV.  Cats with FeLV induced lymphoma typically presented as young cats with masses in the chest cavity, kidney involvement or involvement of the spinal cord region.  Since testing and vaccination for FeLV became widespread, the number of cats with FeLV induced lymphoma has decreased dramatically to where only 14-25% of lymphoma in cats is due to FeLV.   With the decrease in FeLV induced lymphoma in cats, there has been a shift way from lymphoma in cats occurring in the chest cavity and other common sites where FeLV induced lymphoma tended to occur to increased involvement of the intestinal tract, which is the most common location of this from of cancer in cats today.

Feline immunodeficiency virus (FIV) infection can increase a cat’s chance to develop lymphoma approximately fivefold.  Unlikely FeLV virus, which directly can cause cancer to develop in a cat, FIV increases a cat’s potential to develop can by suppression of the immune system.

One study suggests that environmental exposure to second hand smoke increases a cat’s risk of developing lymphoma.  The particular study suggested that any cat with exposure to second hand smoke had a 2.4 relative risk of developing lymphoma and if the exposure was for longer than a 5-year period, the relative risk increased to 3.2.

Although direct proof is lacking, chronic inflammation and diet have been suggested to be possibleDiet and Lymphoma in Cats causes of lymphoma in cats.  This is due in large part to the increased diagnosis of lymphoma involving the intestinal tract of cats.   A common disease of the intestinal track of cats is inflammatory bowel disease.  Many cats with IBD go on to develop intestinal lymphoma.  Since the intestinal tract is exposed largely to what animals eat, the premise is that what sensitizes the intestinal tract to develop cancer must be something in the diet.  Support for this argument is based on several changes made in the diet of cats over the past 20 years or so for other medical conditions such as urinary tract disease.

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Dr Stephen Atwater

Stephen W. Atwater, DVM, MS, Diplomate ACVIM (oncology) is a board-certified veterinary oncology specialist. His professional interests include utilizing emerging therapies for difficult to treat cancers.

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