Are Breast Tumors In Cats Often Cancerous?

Yes, breast tumors in cats are usually malignant.
Breast tumors (mammary tumors) in cats, unfortunately, are usually malignant. Up to nine out of ten breast masses in cats seen by veterinarians are cancerous. Adenocarcinoma (cancer arising from gland cells) is the most commonly occurring mammary tumor. These tumors may involve one or more mammary glands. Other cancers, including sarcoma, which arises from connective tissue cells in the breast, along with other malignancies occur infrequently in cats. Surgical biopsy and examination of the sampled tissue by a pathologist is required to definitively diagnose the tumor. Other problems must be ruled out, including cysts, fatty masses, fibrotic nodules, inflammatory processes and other possible causes of the swellings. Older cats tend to develop breast cancer more frequently than younger ones. Siamese cats are more likely to develop these malignancies than other breeds. Veterinarians believe that unspayed cats have a greater risk for developing breast cancer than spayed cats. Hormones may have a role in promoting these tumors. Surgery is the primary treatment. Although regional excision of the tumor is possible, in most cases better results will be obtained with total mastectomy (breast removal). These tumors may be amenable to treatment with chemotherapy in addition to surgery. Chemotherapy, especially with doxorubicin or cyclophosphamide, can restrain metastatic spread. Radiation treatment is not effective. The prognosis for cats with mammary carcinoma depends on the size of the tumors and the extent to which tumor cells have spread to other parts of the body. If the tumors are less than two centimeters (less than one inch) in diameter and are completely removed with surgery, many cats will live more than three years. Cats with lesions two to three centimeters in diameter may be expected to do well for up to two years. If the tumor mass exceeds three centimeters or has extended into the lymphatics (lymph nodes), then the prognosis is more guarded, with the median survival time being about six months. Cats with cancer-related debility most likely will have metastases (disseminated tumors) in one or more of the following tissues: the regional lymph nodes, lungs, liver, kidneys, adrenal glands, and diaphragm. Many pet owners discover breast masses, only to fail to promptly consult a veterinarian. Early detection and veterinary care are essential ingredients to improving the prognosis. If the diagnosis is verified to be cancer, you may wish to speak with a veterinary oncologist in your area to discuss the prognosis and treatment options. Your veterinarian can arrange a referral for you.