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1 posts from February 2007


Do Pets Get Breast Cancer?

Many pet owners don't realize that pets also suffer from breast cancer. In veterinary medicine, the term that is used is mammary gland tumors, and these tumors are very common in dogs and cats.

Cats generally have 8 mammary glands, arranged in 4 pairs. Dogs usually have 10 glands arranged in 5 pairs, though the number varies with the size of the dog. Mammary gland tumors in dogs and cats can be benign (non-spreading, and cured by surgical removal), or malignant (having the potential to metastasize to other areas of the body and cause death). Cats and dogs differ in the proportion of benign versus malignant mammary gland tumors. In cats, around 90% of mammary gland tumors are malignant. In dogs, less than 50% are malignant.

How can mammary gland tumors be prevented in dogs and cats?

The best way to prevent mammary gland cancer in dogs and cats is through spaying at a young age. To prevent breast cancer, it is important that a pet is spayed before she ever goes into heat. Some owners believe that dogs and cats should have one heat cycle before they are spayed. This is not true! Dogs who are spayed before their first heat cycle have only 0.5% as much chance of developing breast cancer as dogs who are not spayed. That's one-half of one percent; meaning that a dog spayed before her first heat is 200 times less likely to develop breast cancer! After just one heat cycle, the risk rises 16 times higher. Cats spayed before their first heat have 91% less chance of developing breast cancer than unspayed cats. After just one heat cycle, the risk rises.

To be sure your pet is spayed before she goes into heat, you will want to have the surgery performed before she is 6 months old. Around 4-5 months of age is a good time to have your pet spayed, as vaccinations are generally completed by 4 months.

Detecting mammary gland tumors

Just like in people, performing breast exams in dogs and cats is very important. Early detection is key. For example, cats with mammary tumors removed when the tumor is less than 2 centimeters in size have a median survival time of 4 1/2 years, while cats with tumors removed that are bigger than 3 centimeters in size only have a median survival time of 6 months.

Once your dog or cat is 5 years old, perform a mammary exam on her once a month. Gently feel the tissue under and around each nipple. Very small mammary tumors often feel like a bb pellet under the skin. If you feel even a tiny lump or firm area, bring your pet to the veterinarian immediately.

Treatment of mammary gland tumors in pets

The main treatment at this time is surgical removal. Depending on the situation, your pet may have only the affected mammary gland removed, several glands in the area, or all the glands on that side of her body. The tumor that is removed will be sent to the lab for a biopsy to tell you if it is benign or malignant. If the tumor is malignant, you may want to ask your veterinarian for referral to a veterinary oncologist for further advice and treatment.

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