Intestinal Lymphoma (leukemia)

Lymphoma in cats is classified based on the anatomic area that seems most prominently affected by the tumor. In cats, the most common feline form of lymphoma is currently intestinal. This was not always the case. Years ago, prior to the widespread use of the feline leukemia vaccine, the mediastinal form (a tumor in the chest cavity) was the predominant lymphoma form and the leading cause of lymphoma was the feline leukemia virus. 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.

Intestinal Lymphoma

Intestinal lymphoma is a type leukemia that infiltrates the bowel and results in severe diarrhea. It is now the most common form of lymphoma in cats. The average patient is an elderly cat with a history of vomiting, diarrhea, weight loss, appetite loss or any combination thereof.  An actual mass may develop with intestinal lymphoma or the tumor may be more infiltrative. A mass can cause obstruction in the intestine and lead to a crisis that must be resolved surgically.

Although a diagnosis of intestinal lymphoma is best made by biopsy a presumptive diagnosis is often made on the basis of an ultrasound eximation and laboratory tests. If a mass is located, it is important to understand that no matter how localized the tumor appears to be, simply removing the mass is not going to be curative; some kind of chemotherapy is necessary for best chance at long-term survival.

The more infiltrative forms of intestinal lymphoma do not create actual growths; instead the intestine may only be abnormal under the microscope. It is very difficult to distinguish inflammatory bowel disease from lymphoma even with a biopsy. A biopsy however can distinguish between a highly malignant blastic cell type and a more mature cell type (small cell lymphoma). In our experience the blastic form has a poor response to all types of therapy, while the mature cell form is highly responsive for one to 4 years.