Not only is October Adopt-A-Shelter-Dog Month, it’s also Breast Cancer Awareness Month. Although these two subjects aren’t typically associated with each other, dogs can get breast cancer – referred to as “mammary cancer” in the canine world – just as humans do.
Fortunately, mammary cancer is one of the most preventable types of cancer in dogs since it rarely occurs in female dogs that were spayed before their first heat.
Gerald Post, a veterinary oncologist, told ABC News, “It’s important for owners to spay female animals before the animal first goes into heat, because each following heat cycle increases the risk of developing the cancer.”
Mammary cancer is more common in five- to 10-year-old female dogs that have not been spayed, because with every heat cycle, their bodies endure a 60-day hormonal pregnancy regardless of whether or not they breed.
Veterinarian Michael Watts wrote in the Culpeper Star-Exponent, “This hormonal cycle continuously stimulates the mammary tissue for at least four months of each year. The constant stimulation leads to very high rates of cancer. Fortunately, 99 percent of canine breast cancer can be prevented by spaying young dogs.”
Mammary tumors are the most common type of tumors found in female dogs that were never spayed. They can be small, benign nodules or large growths that can spread to the lungs. Approximately half of the mammary tumors found in dogs are cancerous, which is comparable to the ratio of malignant breast tumors found in women.
As with breast cancer, mammary cancer can often be successfully treated if it is caught soon enough. Pet parents can perform mammary exams to check their dogs manually for any suspicious new lumps or growths. “You can palpate the mammary glands — give them a good feel once a week or once a month,” Post told ABC News.
Mammary tumors can develop as a solid mass or multiple swellings, according to Race Foster, DVM, on peteducation.com. “When tumors first appear they will feel like small pieces of pea gravel just under the skin. They are very hard and are difficult to move around under the skin. They can grow rapidly in a short period of time, doubling their size every month or so.”
Using both your eyes and hands to examine your dog could mean earlier detection and successful treatment. If you see or feel anything out of the ordinary, you should take your dog to the vet immediately.
As with other types of pet cancers, veterinarians usually diagnose mammary cancer on the basis of the dog’s medical history and physical exam. According to the American Veterinary Medical Association, your vet may want to run additional tests, such as x-rays, blood tests and ultrasound exams in order to confirm the diagnosis. A biopsy of the mammary tissue is usually necessary to help determine if the tumor is malignant.
Unless the dog is very old, surgical removal of the tumor is usually recommended. If the surgery is performed early enough on malignant tumors, the cancer can be completely eradicated in half of the cases. In some cases, the mammary glands must be removed.
Removal of a dog’s mammary glands is not like a radical mastectomy in humans – the surgery is easier and the recovery time is faster. “In humans, this type of surgery would affect the underlying muscle tissue, which complicates the recovery,” Dr. Foster wrote. “In the dog, however, all of the breast tissue and the related lymphatics are outside of the muscle layer, so we only need to cut through the skin and the mammary tissue…Although this is truly major surgery, suture removal usually occurs in 10 to 14 days, with normal activity resuming at that point.”
Chemotherapy is not usually successful in treating mammary cancer, so it is not widely used. The effectiveness of radiation therapy has not been researched. Some anti-hormonal drugs are being tested.
There is not much that can be done to prevent many cancers in dogs, but mammary cancer is the one exception. If all female dogs were spayed before their first heat, canine mammary cancer could actually cease to exist.