Points on Pets: Spaying dog may fix her against breast cancer
Nov 16,2007 00:00 by R.G._Elmor_DVM

Q: We recently obtained a beautiful mixed-breed dog from our local pet shelter. We do not know how old she is nor do we know if she has been spayed. The counselor at the shelter has encouraged us to have our veterinarian check to see if our dog has been spayed and, if not, to have the surgery done. One of the reasons given to us for having our dog spayed is that the surgery decreases the chance that our dog will develop breast cancer later in life.

Is there any real evidence that spaying does decrease the incidence of breast cancer in dogs? Are any breeds of dogs more likely to develop breast cancer than other breeds?

A: Unfortunately, mammary gland tumors or breast cancer is very common in female dogs, particularly in bitches that have not been spayed and that are greater than 6 years of age. It has been well-documented that spaying dogs prior to their first heat periods dramatically reduces the risk of mammary gland tumors later in life. In fact, it has been estimated that bitches spayed prior to any reproductive activity have 200 times less chance of developing mammary gland tumors than intact female dogs. It has been estimated that spaying dogs following one heat period reduces the risk of mammary gland cancer by about 12 times.

Female dogs spayed after reaching maturity, or about 2 to 3 years of age, have about the same risk of developing mammary gland tumors as intact bitches. Spaying after breast cancer has been diagnosed usually does not extend the dog's life. However, early spaying does seem to reduce the incidence of mammary gland tumors dramatically.

Although mammary gland tumors can develop in any breed of dog, they are most commonly reported in cocker spaniels, dachshunds, German shorthaired pointers, German shepherds, poodles, beagles, Labrador retrievers and Pekingese.

Although most mammary gland tumors can be diagnosed by looking at and feeling the glands, most veterinarians advise taking biopsies to determine the exact type of cancer involved. Because mammary gland cancer often spreads to other parts of the body, chest and abdominal X-rays are also often recommended. Most mammary gland tumors should be removed as soon as they are diagnosed. Allowing a mammary gland tumor to remain increases the chance that it will spread to the lungs or the abdominal organs. Any abnormal swellings of the mammary glands should be examined by a veterinarian as soon as first noticed.

You should have your veterinarian look at your new dog as soon as possible. He or she will advise you about recommended procedures and a complete wellness program designed specifically for your dog.

Q: We have found several horn-like growths on our old dog's body recently. These growths can be easily removed with steady pressure with the thumb at their bases. A small ring is left when the growths are removed. What are these strange growths. Are we harming our dog by removing them?

A: It is most likely that the horn-like growths on your old dog's body are sebaceous cysts, also called epidermoid or keratinous cysts. These develop as the result of degenerative changes in hair follicles and due to injuries to the skin.

While pinching off sebaceous cysts is usually not harmful for the dog, this usually only provides temporary relief. The cysts usually regrow after a short period of time. Large cysts can be removed surgically. You should have your dog examined by your veterinarian. He or she will give you a diagnosis and treatment recommendations.

Send an e-mail or write to Pets, P.O. Box 120190, San Diego, CA 92112-0190. Only questions of general interest will be answered in this column.

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