Infection and Tumors of the Breasts in Cats
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
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.