Breast Cancer in Dogs and Cats

Yes, animals get Breast Cancer too….

Breast Cancer in Dogs

breats-1Breast cancer, also known as mammary gland tumors and mammary cancer, is the most common cancer in female dogs. Breast cancer is possible in male dogs, but is not as common because the mammary glands exist in a very primitive state.  “Tumors” are swellings, masses or growths of new tissue that are often referred to as “cancer” or “neoplasms.”

These tumors can be malignant or benign. “Malignant” tumors are those that tend to progressively worsen over time and, without treatment (and often with treatment) almost always eventually result in death. They are invasive, grow uncontrollably and spread to other areas of the body. “Benign” tumors are those that are not malignant – in other words, they typically do not invade nearby tissue, grow uncontrollably or spread widely.

Dogs with breast cancer often don’t seem to know they have it during the early stages. Certain types of breast cancer, such as inflammatory carcinoma, are very aggressive and can cause the affected mammary gland to ooze, abscess, and become extremely painful. But again, in most cases, the affected dogs seem oblivious to their condition.

What causes breast cancer to develop in dogs remains a mystery. However, it is clearly dependent on hormones such as estrogen and progesterone. Did you know that most breast cancers are preventable by spaying your pet? Compared to unsprayed dogs, the risk for malignant tumors in dogs spayed before their first heat is 0.05%; after the first heat, it is 8%, and it rises to 26% if the dog is spayed after the second heat.

The bottom line is that if you do not plan to breed your dog, spay her before her first heat, and in all dogs, do regular breast exams to check for lumps.  Please report anything unusual to us.

Breast Cancer in Cats

Did you know that cats get breast cancer too? In fact, mammary cancer is the third most common cancer in cats.breast This type of cancer is likely to develop 1 in 4,000 cats. While this is about half the rate of dogs, when cats develop mammary cancer it is often fatal. If mammary cancer is caught early, the treatment is more often successful.

Which cats are at risk for developing mammary cancer?

Any adult female cat can develop mammary cancer, but the average age is usually 10-14 years of age. Siamese cats appear to have a genetic predisposition for developing mammary cancer and are twice as likely to develop it as other breeds. Unspayed females are at a much greater risk of developing mammary cancer. Female cats that were spayed after having heat cycles, with or without having kittens, are also at a greater risk than a cat that was spayed before her first heat cycle. Although rare, mammary cancer can occur in male cats.

Treatment and Prognosis

Like dogs, the best treatment is to have all mammary tumors removed. However, chemotherapy can be an option as well. Prognosis for pets with breast cancer will depend on tumor size, whether ulceration and/or spread to lymph nodes and lungs has occurred, and the histological grade of the cancer on tissue biopsy. The cell types seen on biopsy will determine long-term treatment plans and prognosis.

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