This article will discuss the rates, causes , #1 prevention, and age, breed and sex predilection of mammary tumors in dogs.

Female dogs are at a high risk for developing malignant mammary tumors. Most of the malignant mammary tumors are adenocarcinomas. This means that they originate in the glandular tissue. Some may be inflammatory carcinomas, sarcomas and carcinosarcomas.  Mammary tumors can be small bumps or large growths.

Dog Breast Cancer Rates

Advanced canine breast cancer

Mammary tumors are the most common tumors in non-spayed female dogs. Of all malignant tumors found in female dogs, 50% are mammary tumors. Of the mammary tumors that develop in canines, half are benign.

Mammary cancer is the second most common cancer overall. It is estimated that it affects 160 of every 100,000 dogs per year, which translates to over 118,000 dogs annually.

Canine Adenocarcinoma Causes and Prevention

The risk for developing benign mammary tumors has been linked to the female reproductive hormone progesterone. Progesterone is the hormone responsible for the progression of pregnancy. Spaying significantly decreases the risk of developing these tumors.

Spaying non-breeding female dogs before they are 1 1/2 years of age is the most substantial preventive measure. Breast cancer is very rare among females spayed before their first heat cycle. The risk of malignant mammary tumors in dogs spayed before their first heat cycle is 0.05%. The risk increases to 8% for dogs spayed following their first heat, and jumps to 26% when spayed after their second heat.

Canine Breast Cancer Age, Breed, & Sex Predilection

  • Male dogs rarely develop mammary tumors, but when they do, the tumors tend to be very aggressive, and result in a poor prognosis for the dog.
  • Mammary tumors are most common for non-spayed, middle-age females between the ages of five and ten.

Every dog owner should know about the various types of cancer. Our new dog cancer book gives you all the details.

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