There are many differences between breast cancer in a dog or cat and breast cancer in a human, but unfortunately, there are tragic similarities as well — suffering, difficult choices, and the possibility of death. However, with early detection and appropriate treatment, cat and dog breast cancer can be successfully treated. Understanding risk factors and when to consult your vet can help you protect your beloved pet.
Causes and Prevention
Both cats and dogs can develop mammary tumors. In dogs, about 50% of these tumors are benign or noncancerous, but mammary cancer is still the most common malignant tumor for dogs and rates of breast cancer overall are extremely high among canines.
For cats, breast cancer is the third most common cancer. Although feline malignant mammary tumors occur at half the rate they do in dogs, breast cancer is much more likely to be fatal for cats.
Both dogs and cats can be genetically predisposed to breast cancer. Among felines, Siamese cats develop the disease twice as often as other breeds. Breeds of dogs that are more likely to develop these tumors include Poodles, Terriers, Dachshunds, English Spaniels, English Setters, Cocker Spaniels, and German Shepherds.
The good news is that breast cancer is one of the easiest pet diseases to prevent. Spaying could make all the difference. The development of malignant tumors in the mammary glands seems to be directly related to hormones, so having the source of those hormones removed may protect your pet. Veterinarians recommend spaying female dogs and cats early — before 6 months when the first heat cycle is expected. Having female dogs fixed within this time frame can reduce the risk of malignant breast cancer to only 0.5%. With cats, the risk of breast cancer goes down by 91% if a kitten is spayed before their first heat cycle.
Spotting Breast Cancer in Pets
Mammary cancer has no obvious symptoms in its early stages (which is when you need to find it to successfully treat the tumors). The only way you’ll be able to detect tumors is by performing regular mammary exams on your pet at home.
It’s important to check your pet regularly so you get a good idea of what breast tissue of a healthy dog or cat feels like, allowing you to identify anything that appears abnormal. Start with a nice tummy rub to relax your pet. Then carefully rub your hand over the fatty tissue around each nipple and squeeze the tissue a little. If you feel a hard lump the size of a pea or larger, it might be the sign of a tumor. Lactating cats and dogs with mastitis may have similar lumps, but these would go away with antibiotics — if the lumps linger after the mastitis clears up, your veterinarian may recommend testing for cancer.
In cases where the cancer has metastasized, pets can suffer a range of symptoms such as painful movements and bowel disorders.
Diagnosis and Treatment
If mammary cancer is suspected, your vet will need to do a full exam with a complete blood work up and urinalysis. Benign tumors are usually small and have a round shape. Malignant tumors grow larger rapidly and don’t have clear borders. It’s very hard to tell which type of tumor is present until a biopsy or removal of the tumor is done. Lymph nodes may also need to be examined and a chest x-ray done to check whether the cancer has metastasized.
50% of pets that have cancerous tumors removed in the early stages remain disease free for the following year. Cancer drugs for dogs or cats (aka chemotherapy) may also be prescribed for certain types of tumors. If your pet wasn’t previously spayed, your vet may recommend having the procedure done after a mastectomy to help the vet better identify any future tumors that might develop and to reduce the risk of uterine or ovarian cancers.
Pets with cancer may lose their appetite or have other feeding issues. Taking care to ensure they follow a healthy diet can help your pet recover and stay well.
More on Cancer
Cancer in Dogs and Cats
Liver Cancer in Dogs and Cats
Bone Cancer in Cats and Dogs
Reference and Resources
“Mammary Tumors,” American College of Veterinary Surgeons
This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian with respect to your pet. It has, however, been verified by a licensed veterinarian for accuracy.