Skin Cancer in Cats (cont.)

Mast Cell Tumors

Mast cell tumors are single or multinodular growths, usually less than 1 inch (25 mm) long. The skin overlying the tumor may be ulcerated. Look for these neoplasms on the hind legs, scrotum, and lower abdomen. About one out of three is malignant. Malignancy is more likely when growth is rapid and the neoplasm is larger than 1 inch. Malignant mast cell tumors spread to distant organs.

In another version of mast cell tumors in cats, the spleen is the organ of choice for the cancer. An enlarged spleen may be palpable and many cats with this form of cancer show up with complaints of vomiting. Surgery is recommended.

Treatment: Cortisone may be given to temporarily decrease the size of mast cell tumors. The treatment of choice is wide surgical removal. Siamese cats may have a predisposition to these cancers.


A melanoma is a malignant neoplasm that takes its name from the brown or black pigment usually associated with it. Some melanomas lack in the gene for pigmentation and are called amelanotic melanomas.

Some melanomas develop in preexisting moles. You should suspect melanoma when a pigmented spot starts to enlarge or spread, becomes raised above the surface of the skin, or starts to bleed. Melanomas may be found anywhere on the skin and may also occur in the mouth.

Treatment: Any suspicious pigmented spot on the skin should be removed. Melanoma spreads widely, often at an early stage.

Uveal Melanomas

These are slow-growing malignant tumors seen in the eyes of older cats. This is the primary tumor found in cats' eyes. The pigment in the eye will change and there might be redness or pain as well. Usually just one eye is affected. Older orange cats tend to get pigment changes in their irises, as well, but this is a benign change. Have your veterinarian examine the eye.

This article is excerpted from “ Cat Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.