Feline Mammary Carcinoma: Another Reason to Spay

Author: Dr. Lillie Davis, DVM, DACVIM (Oncology)

Feline mammary carcinoma is the third most common tumor in female cats, particularly affecting older, unspayed cats or those spayed later in life. These tumors are often aggressive, with Siamese cats being particularly predisposed.

Spaying significantly reduces the risk of mammary carcinoma. Intact females are at a seven-fold higher risk compared to those spayed early. The optimal timing for spaying is before six months of age, reducing the risk by 91%. However, spaying after 24 months offers no protective benefit. Additionally, exposure to progestins increases the risk of developing these tumors.

Over 85% of feline mammary tumors are malignant, with a high likelihood of metastasis to the lungs, lymph nodes, and other organs. Early detection and treatment are critical, as tumors less than 2 cm in diameter have a significantly better prognosis. Unfortunately, once metastasis occurs, survival time is drastically reduced.

Surgery is the first-line treatment, with radical mastectomy (unilateral or staged bilateral) being the preferred method due to its higher success rates. Prior to surgery, full diagnostic staging is recommended (i.e. chest x-rays and abdominal ultrasound). Chemotherapy may be considered post-surgery, particularly for larger tumors or those with aggressive features, though its efficacy in prolonging survival remains uncertain.

For any questions or to discuss specific cases, feel free to contact me directly at Ldavis@pase.vet

For additional details regarding this topic, please contact Rebecca Butterworth at Rbutterworth@pase.vet. She can provide you with a recording of Dr. Davis's virtual RACE-approved continuing education session on Feline Mammary Carcinoma.