Most veterinarians refer to breast cancer as mammary cancer, or mammary neoplasia, or mammary gland neoplasia. These are simply medical terms for breast cancer. The term mammary gland refers to breast tissue.

In cats, breast cancer is the third most common form of cancer diagnosed. It is more common in cats than in humans but still less common in cats than in dogs. Obviously, breast cancer affects primarily female cats. Male cats are rarely affected. Approximately 85% of all breast tumors in cats are malignant. Malignant cancers may occupy more than one mammary gland (breast) and can spread rapidly to other parts of your cat’s body.

The average age for cats to develop breast cancer is approximately 10 years. However, affected cats may be older or younger. I’ve seen breast cancer in cats as young as 5 years and as old as 20 years.

Treatment of malignant breast cancer usually involves surgical removal of the affected gland or glands.  Surgery in these cases is often radical and may involve removing all of the glands on one or both sides of the body as well as the regional lymph nodes. Other treatments include chemotherapy and possibly radiation therapy.

Prognosis for breast cancer in cats is based on several different factors, including the size of the mass, the involvement of lymph nodes, and the individual characteristics of the cancer itself.

Cats that are spayed prior to 1 year of age have a much lower risk of getting breast cancer than cats that are not spayed. In itself, this is a good reason to spay your cat. Added benefits of spaying include removing the risk of pregnancy, complications arising from queening (the process of giving birth), and pyometra (uterine infection). Another benefit is the fact that cat owners do not need to deal with the heat cycle or live with a cat in heat. Spayed cats do not go through heat cycles and do not come into heat as unspayed cats do. For those who have never experienced the antics of a cat in heat, it is not generally a fun experience for the cat owner, though it is a completely normal physiological process for the cat.

Spaying your cat at an early age is the single-most important thing you can do to protect your cat from breast cancer. However, it is also a good idea to check your cat’s breasts for swellings or masses on a regular basis. If found, consult your veterinarian. Early intervention is the most effective means of resolving the situation with a successful outcome.

Dr. Lorie Huston



Beth Overley et al; “Association between ovarihysterectomy and feline mammary carcinoma”; J Vet Intern Med. 2005 Jul-Aug;19(4):560-3.

Rodney Page; “Prognostic Factors for Canine and Feline Mammary Cancer”; World Small Animal Veterinary Association World Congress Proceedings, 2001

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