The short answer is yes, your dog can get breast cancer, better known in canines as mammary cancer. In fact, mammary cancer is the most diagnosed tumor in female dogs that are still intact. Just like with humans, these tumors can metastasize and spread to other areas of a canine’s body.
What are Mammary Tumors (cancer)
They are abnormal replication of cells that make up breast, or mammary, tissue. They can be benign (non-cancerous) or malignant (cancerous). While mammary tumors are almost exclusively associated with female dogs, male dogs can get these tumors too.
What Causes Mammary Tumors
The exact cause for the development of mammary tumors is not known exactly. What is known is that exposure to certain hormones, specifically progesterone which stimulates growth, can cause mammary cells to multiply.
For dogs seven years or older, the risk increases until about the age of 11–13.
Mammary tumors usually strike one in four unspayed female dogs over the age of two. 90% of tumors found are benign and mammary cancer is rare. Females spayed before their first cycle reduce their chance of mammary tumor from 25% to .05%. If spayed between their first and second cycle, the risk of mammary cancer is about 8%.
Types of mammary tumors
- Malignant (cancerous) — About 50% of all mammary tumors are malignant. Of those found to be malignant, 50% of those have already spread to other parts of the body when they are initially found.
- Benign (non-cancerous) — As you may have guessed, the other 50% of mammary tumors found on dogs are benign.
- Hyperplasia or dysplasia — These tumors appear during a heat cycle and will then dissipate once the heat cycle is over.
Breeds that have a greater chance of developing mammary tumors are:
- Boston Terriers
- Brittanys
- Cocker Spaniels
- Dachshunds
- English Terriers
- German Shepherds
- Pointers
- Toy and Miniature Poodles
Signs of Tumors in Dogs
If your pooch isn’t feeling well—like eating less, lethargic, or losing weight, that might be a sign of cancer, among a myriad of other possible ailments.
The most common clinical sign of mammary cancer is one or more palpable masses underneath the skin by any one of the breast areas. These masses range in size but are firm and take on a round-like shape. In some cases, the skin over these masses will break open and could bleed. In other cases, discharge could develop from the mammary glands.
If you notice any newly developed lumps on your dog, get them into your vet’s office sooner than later. They will need to do a biopsy in order to determine if they are benign or malignant.
