Intestinal lymphoma is now the most common form of lymphoma in the cat.  The average patient is an elderly cat with a history of vomiting, diarrhea, weight loss, appetite loss or any combination thereof. Patients are generally older cats (median ages ranging from 9-13 years depending on the study) with a tendency for male cats to be more predisposed to development of the condition than female cats.

An actual mass may develop with intestinal lymphoma or the tumor may be more infiltrative.  An actual mass can potentially cause obstruction in the intestine and lead to a crisis that must be promptly resolved surgically.

Diagnosis of intestinal lymphoma is best made by biopsy and if a mass is present, it can be surgically removed at the time biopsies are taken. Alternatively, the mass can be aspirated (cells removed via syringe) and the cells analyzed in the lab. This may not be as definitive as biopsy but is often adequate; surgery, of course, enables the removal of the growth (if there is one) and relieves the obstruction.

It is important to understand that 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 without a full-thickness biopsy (a full-thickness piece of intestine) obtained via exploratory surgery. A less invasive method of obtaining a sample is via endoscopy, usually adequate for diagnosis but full thickness biopsy samples cannot be obtained this way.

• Cats with intestinal lymphoma treated with prednisone alone have a life expectancy of 45-60 days. Other protocols using multiple drugs yield much better results (see below for details)
   
• Lymphoma is graded by the pathologist reading the tissue sample as either “high-grade,” “low-grade,” or “intermediate grade.”  The grade refers to how rapidly the cells appear to be dividing and how malignant they appear with “high grade” being the most malignant. The grade of lymphoma bears on its response to chemotherapy (see below). It is not possible to determine lymphoma grade from a tissue aspirate; an actual piece of tissue must be submitted for biopsy.  As a general rule with lymphoma, higher grades tend to be more responsive to chemotherapy drugs. With feline intestinal lymphoma, however, it is the low grade cases that are capable of fairly long remissions.

As with dogs, chemotherapy protocols are associated with minimal side effects. Many protocols have been described for the feline lymphoma patient.

• In one study 7 cats were treated with the COP protocol (cyclophosphamide, vincristine, and prednisone).  Of these 7 cats, 6 achieved remission with a median duration of remission lasted 19 weeks. The grade of intestinal lymphoma was not considered.
   
• In one study, 14 cats were treated with cyclophosphamide, vincristine, and methotrexate.  Median survival time was 12 weeks.  The grade of the intestinal lymphoma was not considered.
   
• In another study, 132 cats with lymphoma were treated with COP plus doxorubicin, L-asparaginase, and methotrexate (the “CHOP-like” protocol).  Of this group 125 cats had intestinal lymphoma. Out of the total 132 cats, 67% achieved remission with a 21 week disease-free interval. Another  study using the same protocol on 21 cats with intestinal lymphoma, only 38% achieved remission but these cats had disease-free interval of 40 weeks.
   
• In another study, 25 cats with intestinal lymphoma, 25 of which had “high grade” lymphoma, were treated with COP. Those who achieved complete remission had a 30 week disease-free interval. The overall median survival when all 25 cats were considered was only 7 weeks.
   
• Another study looked at 11 cats with high grade interstinal lymphoma treated with COP plus doxorubicin and L-asparaginase. Only 18% achieved complete remission. Median survival was only 11 weeks.
   
• As for low-grade intestinal lymphoma, a study of 50 cats included 36 treated with prednisone and chlorambucil. Here, 69% achieved complete remission for a median duration of 20.5 months.