Do Mammary Tumors in Dogs Affect the Reproductive System?

Mammary tumors in dogs are very common and can be successfully treated with early detection. Whether or not these tumors affect the reproductive system of your dog depends on the following factors:

  • Age of Your Dog-Mammary tumors are most common in female dogs aged five to ten. Female dogs spayed before their first heat are at the lowest risk for mammory tumors. Mammary tumors occur more rarely in younger dogs. These tumors are rare in male dogs, but when they occur they are more difficult to treat.
  • The Type of Tumor-More than half of all mammary tumors in dogs are benign. Benign tumors are small, smooth, and grow slowly; they may have little to no effect on your dog's reproductive capability. Malignant tumors are cancerous and occur in the breast tissue itself. Malignant or cancerous mammary tumors in dogs grow quickly, have an irregular shape, and attach themselves firmly to the skin or tissue around them. Malignant tumors may cause bleeding and ulceration. Your vet will need to perform a biopsy to determine whether a mammary tumor is benign or malignant.

Affect on Reproductive Capacity

A small benign mammary tumor may have no effect on your dog's reproductive capacity, especially if it is very slow-growing.

A malignant tumor, if detected early and successfully removed, may not affect your dog's reproductive capacity. However, if your dog requires a radical mastectomy, or radiation treatment or chemotherapy, reproductive capacity may be seriously diminished.