Mammary Gland (Breast) Tumors in Dogs
The success rate of surgery depends on the biological potential and the size
of the tumor. Benign tumors are cured. Bitches with small malignant tumors less
than 1 inch (25cm) across have favorable cure rates. Those with large,
aggressive tumors are more likely to have metastatic disease and a poor
The addition of chemotherapy, immunotherapy,
and complete ovariohysterectomy does not improve cure rates, although
chemotherapy may offer some relief in bitches with advanced cancers that cannot
be surgically excised.
Prevention:Spaying a female before the first heat cycle reduces her risk of
breast cancer to less than 1 percent. If she is spayed after one heat period,
her risk is still only 8 percent. After two heat cycles, however, there is no
reduction in risk.
It is important to examine the mammary glands of unspayed bitches every
month, starting at 6 years of age or younger. If you feel a suspicious lump or
swelling, take the dog to your veterinarian at once. Experience shows that many
owners procrastinate for several months hoping that a lump will go away. Thus,
the opportunity to cure many mammary cancers is lost.