by Joshua Keyes DVM

Created on: July 08, 2008   Last Updated: August 16, 2008

Shelby was a twelve-year-old femal calico cat with long, bautiful fur and a gentle disposition. She was much loved by her family, but she had never been spayed. This was difficult for me to understand (how could a loving family fail to spay their cat?) She purred in the exam room during most of her exam while her owners told me about her household antics, chasing felt mice and catching real rats in their barn? It was supposed to be a routine physical exam on a healthy cat, but when I looked at a lump on her underside, I had a sinking feeling. How to tell this doting family that the plum-sized purple lump was going to take this sweet girl away before her time?

Mammary cancer is the third most common type of cancer in our feline friends. It's a disease of middle-aged to older cats. Most patients are unspayed cats of about 10 to 12 years of age. Unlike dogs who often have benign mammary tumors, cats almost always have malignant mammary tumors. They spread quickly and aggressively, first to the closest lymph nodes, then to the lungs and vital abdominal organs. Mammary cancer can also spread to the bones and the neurologic system. In most cats, the cancer has already spread by the time the owner recognizes a mass near the teats.

These tumors are often firm and bluish. They are higly vascular and fragile, prone to erupting and creating a bleeding mess. If they are removed when they are only about 2 centimeters in diameter, the cat may live for 4 more years or longer, but once they get to be 3 centimeters, the patient is probably only going to live for a few months, even if the tumor is removed promptly after that point.

The cat who is spayed young is much less likely to acquire mammary cancer than any counterpart who is spayed after two years of age or not spayed at all. In fact, spaying offers the most protection against this disease if it is done beofore four months of age. But what if you didn't know this and didn't spay your cat in a timly manner and now your cat has a mammary tumor.

Schedule surgical removal as soon as you can. The veterinarian will most likely remove not just the lump, but the whole mammary chain on that side of the body. Pre-surgical blood testing and chest X-rays are almost always recommended. Ask your veterinarian about referral to an oncologist for follow-up chemotherapy. This is becoming increasingly available in more and more areas, even those that are not entirely urban.

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