Infection and Tumors of the Breasts in Cats (cont.)

Breast Tumors

Breast tumors occur frequently in unspayed cats. Eighty percent are malignant (adenocarcinoma). The rest are benign adenomas. Breast cancer is the third most common cancer in cats. Most affected cats are unspayed females over 6 years old. Siamese have an increased risk for mammary cancer, as do cats with the calico pattern. Breast cancer is rare among spayed females, especially those neutered before their first heat cycle. Early spaying reduces the risk factors sevenfold.

Feline breast cancer is a rapidly progressing neoplasm that has a high rate of local recurrence following treatment. It tends to spread widely, with the lungs being the favored site for metastases, as well as local lymph nodes. The typical presentation is a painless, firm, nodular mass in one or more breasts, most commonly involving the first and fourth nipples in line. The skin ulcerates as the tumor advances. A chest X-ray is advisable to rule out lung involvement before embarking on radical surgery.

Progesterone therapy may also increase the risk of breast tumors, including cancers. Avoid the use of progestins to treat skin or behavior problems.

Treatment: Surgical removal is the treatment of choice for all breast tumors. Surgery may appear quite radical, with a very large incision to increase the likelihood of removing all the cancerous tissue. Close follow-up to detect local recurrence after surgery is advisable. Chemotherapy may help to improve quality of life. Secondary infections are common, so most cats end up on postoperative antibiotics.

The success of the operation depends on the stage of the tumor at the time of surgery. The earlier the cancer is discovered and treated, the better the outlook. Prognosis is closely related to the size of the tumor at the time of surgery, with smaller tumors offering the best prognosis. Therefore, when your unspayed female is 3 or 4 years old, begin examining her breasts at least once a month. If you detect a suspicious swelling or a firm lump, ask your veterinarian to examine it.

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