Several types of skin cancer can affect cats. It is important to distinguish a cancer from a benign neoplasm. Signs that a growth might be a cancer are visible enlargement, ulceration of the skin with bleeding, and a sore that does not heal. Physical appearance alone is not always a reliable indicator. Surgical removal or biopsy is necessary to establish an exact diagnosis. The following are the most common malignant skin tumors in the cat.
Basal Cell Carcinoma
This is the most common type of skin cancer in cats. It tends to show up in older cats, often as a single growth on the head. Basal cell carcinomas occur as small nodular growths beneath the skin, often next to each other, producing solid sheets of bumps. They also tend to occur on the back and upper chest. Basal cell tumors enlarge locally and spread by direct extension. They do not usually metastasize.
Basal cell tumors are most commonly seen in Siamese and domestic longhair cats. Rarely, basal cell tumors become malignant. This occurs in Persians cats primarily, so any lumps on a Persian's head should be checked out right away.
Treatment:Wide surgical removal prevents recurrence.
Squamous Cell Carcinoma
This neoplasm, also called an epidermoid carcinoma, appears as a cauliflower-like growth or a hard, flat, grayish ulcer that does not heal. Size varies. These cancers tend to occur around body openings and in areas of chronic skin irritation. Hair may be lost because of constant licking.
A peculiar form of squamous cell carcinoma involves the upper and lower lips of cats who suffer from a condition called indolent ulcer. Another type involves the ear tips and nose of cats with white hair in these areas who are exposed to ultraviolet sunlight.
Oral squamous cell carcinomas tend to occur in older cats, often near the base of the tongue. It is suggested that while grooming, cats may lick off carcinogens that then lodge near the tissues of the mouth. Your cat may have loose teeth or go to his food and water bowls but not eat or drink. Drooling and bad mouth odor are common. This cancer has been associated with exposure to secondhand cigarette smoke, possibly a canned food diet, and possibly the use of flea collars.
Treatment:Early detection and treatment of squamous cell carcinoma is important. This neoplasm is capable of spreading to other locations. Treatment may involve a combination of surgery and radiation, with chemotherapy included in some protocols.
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.
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.