Dr. Trisha Joyce, a veterinarian for New York City Veterinary Specialists, knows how lethal mammary disease — cancer of the mammary glands — can be in cats. The first case of mammary cancer she saw was with a cat that was brought in with a lump. “We removed the tumor and the cat was fine. Six months later, the couple and the cat were back. Another tumor had appeared. This one had ulcerated, and it was too late to treat it.”
Since that time, Joyce has counseled cat owners on how to prevent and detect mammary disease, and how to proceed once it’s been diagnosed. Below, she shares her advice on each of these.
Mammary cancer is the third most common cancer among cats, and it is also one of the most preventable. “First and foremost, spay your cat,” says Joyce. Kittens spayed before they are 6 months old have a 91-percent reduction in their risk of developing the disease. Kittens spayed before they are 1 year old have an 86-percent risk reduction. In contrast, cats spayed before the age of 2 have only an 11-percent reduction, with no reduction of risk at all after age 2.
Mammary tumors are most commonly found in unspayed cats between 10 and 12 years old. Siamese cats are more likely to develop the disease, and the onset is typically earlier. Male cats very rarely develop mammary cancer, although it can happen — and is usually aggressive when it does.
When Joyce meets owners of unspayed cats, she encourages them to perform regular mammary exams at home. The idea is similar to the self-exams that women are taught to perform by their gynecologists in order to become familiar with their own breast tissue. “If you know how your cat’s mammary glands feel when they’re free of tumors, it’s easier to catch a growth if one develops,” she says. The tumors are not painful to the touch, though cats that don’t like to be stroked may try to get away.
To examine your fluffy friend, run your hand over the fatty tissue around her nipple. “Just rubbing the belly is too superficial. Squeeze the tissue a little, almost like milking a cow. You’re looking for a lump like a little hard pea, or sometimes bigger,” says Joyce. Finding a lump is a good reason to visit the veterinarian as soon as possible: Doctors estimate that as many as 90 percent of mammary tumors in cats are malignant.
Other than these telltale lumps, mammary cancer is asymptomatic in its early stages. If it metastasizes, the cat may go on to develop health problems related to where the cancer has spread.
Diagnosis and Prognosis
Because feline mammary tumors are so likely to be malignant, prompt removal of the entire mammary chain on the effected side is most veterinarians’ treatment of choice. Mammary surgery is less complicated than mastectomy in women, as a cat’s breast tissue is outside of the muscle layer. Prognosis is best the earlier the cancer is caught, and the smaller the tumor is. Surgery yields a disease-free year for 50 percent of cats, while almost one-third of cats will go two years without the development of additional tumors. Surgery is often followed by a course of chemotherapy.
In advanced cancers that have metastasized, surgery may still be performed to reduce the impact of the tumor and improve quality of life. Sometimes, though, a metastasized mammary tumor means it’s time to let your cat go. “The tumors can become ulcerative, making just moving around extremely uncomfortable, or if they spread to the lungs or the bones and make breathing or walking very hard, the most humane option may be euthanizing,” says Joyce.
Mammary cancer in felines is fairly common, but it is also preventable, and most often not immediately fatal. With early detection, surgery and chemotherapy, your cat may have additional good years to spend with her loved ones.