We already know there are incredible benefits to spaying or neutering your cat. Today we’re discussing mammary tumors in cats—and how spaying significantly decreases mammary cancer in cats. Here’s what you need to know.
What is mammary cancer in cats?
Cats have mammary glands and nipples running parallel along both sides of the belly. Mammary tumors can arise in these glands just beneath or next to a nipple. Here are some of the sobering statistics about breast cancer in cats:
- Tumors originating in the mammary glands account for the third most common type of feline cancer, after lymphoma and skin cancer.
- Mammary cancer occurs 95 percent of the time in female cats.
- Mammary cancer is the most frequently diagnosed feline cancer in cats that are older than 10 years.
- Approximately 85 percent of feline mammary cancers are lethally malignant.
Recognizing mammary tumors in cats
Due to the relatively inaccessible area where mammary tumors are found (how many cats love to have their bellies touched?), breast cancer in cats often remains undiscovered until the disease has progressed.
Mammary tumors in cats usually start in the glands just beneath or next to the nipple. It may feel like a small, firm nodule, similar in size to a BB.
To be proactive about your cat’s health, you can palpate your cat’s underside in the areas of the mammary glands and nipples on a weekly basis to detect any obvious masses or lumps. This is particularly important if your cat falls into one of these at-risk categories:
- Spayed after her first heat cycle: As we’ll discuss in more detail, spaying young significantly decreases a cat’s chances of developing mammary cancer.
- 10+ years old: The average age of cats with mammary cancer is between 10 and 12 years.
- Siamese: This cat breed is twice as likely to develop mammary cancer as other breeds, and at a younger age.
Another sign to watch out for is your cat excessively grooming the area of a growth. There may also be a strong odor associated with an infected tumor.
Diagnosing mammary tumors in cats
All mammary tumors or masses are not created equal. Mammary tumors can be non-cancerous (benign) or malignant (cancerous). If you feel or see a lump or nodule on your cat’s underside, make an appointment with your veterinarian right away.
Your vet will likely want to perform a fine needle aspirate (FNA) or remove a portion of the affected tissue for a biopsy under either heavy sedation or general anesthesia. They may also take chest and/or X-rays along with abdominal ultrasound imaging to determine if the mass has spread to other parts of the body like the lymph nodes and internal organs such as the lungs or liver.
These tests, along with others pending the situation, help the vet to determine whether the mammary mass in question is benign or malignant. Knowing this helps to dictate how to manage or treat it. It also provides more information regarding your cat’s overall prognosis, or projected survival time.
Unfortunately, most mammary tumors in cats are malignant.
Identifying mammary tumors is not as simple as determining whether they are benign or malignant. A veterinary pathologist can use the tissue sample from the FNA or from a removed mass to perform a histopathology on it; this helps to determine the type of mammary tumor it is. Carcinomas are the most common type of mammary cancer in cats; other types include adenocarcinoma, adenomas, and osteosarcomas.
Treating mammary cancer in cats
Depending on if the cancer has spread, the vet will refer you to a veterinary oncologist to determine the best way to manage or treat your cat’s cancer. Veterinarians can perform a mastectomy, or removal of the mammary tissue, on your cat and/or start chemotherapy treatment. The good news is, if caught early (where the tumor is smaller than 2 cm in diameter), odds of survival improves to three or more years.
Preventing mammary cancer in cats
Unlike some types of feline cancer, the development of mammary cancer isn’t highly influenced by genetics or environmental factors. Instead, it is significantly influenced by a cat’s hormones.
Why spaying decreases mammary cancer in cats
In female cats, the onset of mammary cancer is tied to the release of the estrogen and progesterone hormones. When a cat is spayed, her ovaries are removed and she no longer produces estrogen. This is why veterinarians strongly recommend spaying your cat before she enters her first heat cycle, which can be as early as 3-4 months of age.
According to Cornell Feline Health Center, spaying before the age of six months can reduce a cat’s risk of mammary cancer by as much as 91 percent. And spaying before 1 year of age can reduce the risk up to 86 percent.
With odds like these, there’s really no reason not to spay or neuter your pets early on in life!
What if I don’t know when my cat was spayed?
Unfortunately, you can’t always control how old your cat was when she was spayed. If your cat was spayed past the age of 1 or you are unsure how old she was when spayed, it’s a good idea to know how to recognize a potential mammary tumor—especially if she is older than 10 years of age.
The best way to ensure that mammary cancer is caught and addressed early is by performing routine mass checks at home by feeling your cat's belly during quality time and by scheduling your wellness checks with your veterinarian. It is recommended that senior cats visit their veterinarian at least twice a year for wellness checks and more often if they have chronic medical issues that require more frequent veterinary care.
