The Purrfect 10: Things To Know About Breast Cancer in Cats

We love reading and researching anything and everything about cats, and wanted to find a fun and unique way to share the interesting facts we learn with you! Since top 10 lists are very popular in the blogosphere, we created The Purrfect 10 as a way to present 10 educational or fascinating tidbits about a wide variety of cat-related topics, everything from health issues to cat breeds to famous felines.

October is Breast Cancer Awareness Month. Every one of us knows someone whose life has been changed by this dreaded disease, but you might be surprised to learn that it's also frighteningly common in our beloved cats. Here's what you need to know...

1) Breast cancer is the third most common cancer in cats (after lymphoma and skin cancer), and over 85% of mammary tumors are found to be malignant.

2) Most of the time the patient is female, either unspayed or spayed well into adulthood. The average age at onset is 10-12, but these tumors can strike at any age with reported incidents from 9 months to 20 plus years old.

3) Cats have two “chains” of four mammary glands and nipples running parallel on each side of their belly. The first sign of breast cancer a cat owner might notice is a lump in, on or near one of these glands in the shape of a pebble or dried pea. These tumors, most commonly adenocarcinomas, can spread rapidly to adjacent glands, the nearest set of lymph nodes and beyond. Unfortunately it can be months before a growth is detected because in it's initial stage it can be very hard to feel, it won't be painful to your cat, and won't show any obvious clinical signs.

4) Cat parents should check their cat's mammary area for lumps on a regular basis. (A great excuse for extra tummy rub time!) When found, these tumors need to be removed as soon as possible, followed by chemotherapy. Left alone, they get larger and harder and eventually ulcerate the skin, resulting in a strong odor as infection sets in. Small tumors might be removed via lumpectomy, but your vet may remove the entire mammary gland and nearby lymph nodes, if not the entire chain on that side (the feline version of a mastectomy), the surgical method of choice because it significantly reduces the chance of local tumor recurrence. If caught early and a cure is possible, the opposite side may be removed after a few weeks.

5) Life expectancy following removal of a mammary tumor varies, with tumor size being the most important factor. According to the Ohio State University Veterinary Medical Center, cats with tumors larger than 3 cm in diameter have a median survival time of 4 to 6 months; cats with tumors 2 to 3 cm in diameter have a median survival time of about 2 years, and cats with tumors less than a 2 cm in diameter tumor have a median survival time of over 3 years. Early diagnosis and treatment is key, but even when tumors are caught early and appear to be successfully treated, the long term prognosis is guarded. Over 60 percent of tumors that have been removed will redevelop within 12 months.

6) While very rare (less than 1% of cases), male cats can also get breast cancer, and any suspicious lumps should be reported to your vet.

7) Sex hormones are the greatest risk factor for mammary tumors in cats, so spaying at an early age is the most significant way to prevent breast cancer: spaying prior to 6 months results in a 91% reduction risk, and before one year old an 86% reduction.

8) Siamese have twice the risk of developing breast cancer than other breeds, developing tumors at a younger age and with higher rate of lymphatic invasion than other cats. Persians also develop tumors frequently.

9) In Scandinavian countries mammary tumors are especially prolific because domestic cats are not commonly spayed and the female hormone progesterone is often used to prevent pregnancy. In fact, until 1988 it was illegal for Swedes to remove the reproductive organs of their dogs and cats unless medically necessary!

10) Pulmonary metastasis (spread of the cancer to the lungs) is the most common cause of mammary-cancer related deaths, and cats presenting with advanced lung involvement at diagnosis have a reported median survival time of only one month.

Have you ever had a cat diagnosed with breast cancer?