Mammary Cancer

What is mammary cancer? Mammary cancer ranks as the third most common form of cancer affecting cats. In fact, about 90 percent of mammary tumors are malignant. That’s because the cancerous cells seem to spread to nearby lymph nodes. They also can infiltrate the brain, chest, lungs, bone and spleen.

How does my cat get mammary cancer? It is unclear how this cancer develops, but veterinary oncologists suspect that hormones play a part. Most cases of this type of cancer strike females who are not spayed and 10 years or older, but even male cats are not risk free.

How do I know if my cat has mammary cancer? You may notice what feels like a hardened pea or small pebble on your cat’s body when grooming or petting, most frequently near a nipple. Undetected, the tumors can grow in size and density and may burst and produce an infected ulcer that bleeds and smells rotten. Your veterinarian will perform a physical exam, take xrays and run blood and urine tests, and palpate the suspected tumors. Your vet will also need to take a tissue biopsy to confirm the diagnosis of mammary cancer. Tests will be able to assess the size and progression of the cancer. A cat with Grade I mammary cancer has a better chance for survival than Grade II or Grade III. Cats with Grade III rarely survive beyond a year, even with surgery.

What can I do about mammary cancer? The earlier the cancer can be detected and treated, the better the prognosis for your cat. Most cats with small-sized tumors live, on average four or five more years versus only an average of six months for cats who have large-sized tumors. Surgical removal of the tumor is a common treatment, but it may be necessary to also remove surrounding tissue. Chemotherapy is advised following surgery, especially when the surgery reveals that the cancer has spread to the lymph nodes.

Is there anything I can do to prevent my cat from getting mammary cancer? Having your kitten spayed at an early age seems to reduce the risk of this form of cancer. In fact, studies indicate that kittens spayed by 6 months are far less likely to get mammary cancer than those spayed at age 1. If you delay and spay your cat after age 2, this procedure does not seem to reduce the risk of this cancer from developing.

Are there certain breeds that get mammary cancer more often? Yes. Inexplicably, Siamese develop mammary cancer at greater rates than other breeds and at younger ages.