Mammary Gland (Breast) Tumors in Cats

Feline Mammary Gland (Breast) Tumors

Mammary gland tumors, commonly referred to as breast tumors or breast cancer, are a type of cancer that arise from breast tissues. These tumors are similar to breast cancer in women, and they can be lethal in cats. Approximately 90 percent of these tumors are malignant, which means they can spread. Mammary tumors in cats can rapidly spread to adjacent glands and lymph nodes.

The cause of mammary tumors is not well understood. Hormones such as estrogen and progesterone play an elusive role in the development and progression of these tumors. They occur in both intact (non-neutered) and spayed cats and it is the most common cancer of female cats, with two cases per thousand cats at risk, constituting over 50 percent of all cancers. Mammary gland tumors occur most commonly in females; they are rare in males.

The average age that cats develop these tumors is 10 to 14 years. Any breed of cat may develop these tumors, but breeds that appear to be at increased risk are Siamese. Siamese cats develop tumors at an earlier age – the average is 9 years.

Timing of ovariohysterectomy, which is removal of the ovaries and uterus and commonly called neutering or spaying, significantly impacts development of mammary gland tumors in cats. Cats spayed prior to their first estrus cycle (heat cycle) have less than a one percent risk, those spayed between the first and second estrus have an 8 percent risk, whereas those spayed after their second estrus cycle develop these tumors as commonly as cats that are not spayed.

Body weight may influence the development and progression of these tumors.

What to Watch For

Diagnosis of Mammary Gland Tumors in Cats

Treatment of Mammary Gland Tumors in Cats

Home Care and Prevention

If you note a mass in your cat’s mammary glands, have her examined by a veterinarian as soon as possible. Malignant masses that have gone undetected for long periods and are large are more likely to spread.

If your cat has a large, ulcerated, bleeding mass keep her indoors to keep the area clean and lessen the potential for infection before seeing your veterinarian.

Have your pet spayed or neutered at an early age to decrease the risk of this type of cancer. Avoid the use of synthetic hormone products to control heat cycles as they may increase the risk of your cat developing this type of tumor.

Take your cat to your veterinarian for regular examinations so that tumors can be detected early when they are more likely to be completely removed. This is especially important if you have an older cat that is at increased risk for this type of cancer.

In-depth information on Mammary Gland Tumors in Cats

Swelling of the breast tissue can be related to a number of conditions – both normal and abnormal. For example, normal hormonal changes associated with the female reproductive cycle in nonspayed females lead to enlargement of the mammary glands. Pregnancy is of course related to glandular development. Inflammation, hyperplasia (excessive growth), and cancers are examples of abnormal growth. When mammary glands are enlarged or swollen, a veterinarian will consider a number of diagnoses.

Veterinary care should include diagnostic tests and subsequent treatment recommendations. Medical tests are needed to establish the diagnosis, exclude other diseases, and determine the impact of the mammary gland tumor on your cat.

Diagnosis In-depth

Your veterinarian may recommend additional diagnostic tests to ensure optimal medical care. These are selected on a case-by-case basis.

Treatment In-depth

Prognosis for Breast Cancer in Cats

The larger the tumor at time of removal – the poorer the prognosis. Small tumors less than -0.8 inch (2 cm) have been studied and are associated with a life expectancy of approximately 4 1/2 years. Larger tumors, more than 1.2 inches or 3 cm in diameter) are associated with a life expectancy of 6 months. Therefore, it is important to remove tumors as early a possible when they are as small as possible.

Follow-up Care for Cats with Breast Tumors

Optimal treatment for your cat requires a combination of home and professional veterinary care. Follow-up can be critical. Administer prescribed medications as directed, and be certain to alert your veterinarian if you are experiencing problems treating your cat.

Specific optimal follow up veterinary care for mammary gland tumors in cats and cats involves the following: