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Mast Cell Tumors in Cats

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Lili Duda, VMD
Last Modified: November 1, 2001

Dear OncoLink "Ask the Experts,"
I need specific information on mast cell tumors in cats. My cat was presumed to have a mammary tumor, and your information was very helpful. After surgery and biopsy, however, she was diagnosed with a mast cell tumor and I am now unsure as to what more should be done. The borders appeared to be free and the report stated that prognosis was moderately optimistic, but I would like to know more about this cancer.  
Thank you.

Lili Duda, VMD, Editor of the OncoLink Veterinary Oncology Section, responds:

Dear Reader,
Thank you for your interest and your question.

Mast cell tumors are the second most common skin tumor, and the most common tumor of the spleen in cats. Most mast cell tumors in the skin of cats have a relatively benign behavior. Complete removal of the tumor(s) via surgery is usually adequate treatment. Cats can develop multiple mast cell tumors, so they should be examined periodically for any new "bumps."

However, mast cell tumors in the skin can occasionally be due to metastasis (spread of cancerous cells) from a tumor in the spleen. Therefore, a complete evaluation of a cat with a mast cell tumor should include blood work (complete blood cell count and blood chemistries) as well as either X-rays or ultrasound of the abdomen to evaluate the spleen and liver.