Mammary Tumors in Dogs

50% of all tumors found on a dog are mammary tumors. They are most commonly found on unspayed or intact female dogs but can also be found in spayed dogs or even, rarely, in male dogs. Age also seems to play a role in the incidence of mammary tumors as older dogs are much more likely to develop them. Certain breeds are also more predisposed to them which indicates there may be a genetic link.

What causes mammary tumors in dogs?

The specific cause of mammary tumors in dogs is still unknown; however, hormones likely play a significant role in their development. It has also been demonstrated that the consumption of red meat, obesity before one year of age, and obesity a year before diagnosis are all associated with an increased risk of development.

Clinical Signs of Mammary Tumors in Dogs

The last two mammary glands (closest to the tail) are usually involved more than the other three sets. They often start out feeling like a small, firm nodule, almost like a BB pellet. There can certainly be more than one nodule or mass per gland.

In advanced stages, the masses become larger and may even become an infected, open, draining sore. If malignant, one of the most common areas of the body that they spread to are the lymph nodes.

How are mammary tumors diagnosed?

Mammary tumors are usually found just by feeling along the mammary chains either by a very

astute dog owner or a veterinarian during a routine physical exam. The next step is usually some screening blood work (chemistry and CBC or “Complete Blood Count”) and urinalysis to evaluate the dog’s overall health status. X-rays and ultrasound are also excellent diagnostic tools and are recommended to check for any additional tumors and/or other abnormalities.

A fine needle aspirate (FNA) may be the next recommended stop. An FNA is a relatively minor procedure where a tiny needle is injected into the mass and cells are withdrawn to be examined under the microscope in the office or sent out for a pathologist to read and make recommendations.

Treatment Options for Dogs with Mammary Tumors

Instead of performing an FNA in the office, veterinarians often recommend surgical removal and sending off some of the tissue as a biopsy rather than just a few cells.

There are different types of surgical removal options ranging from just a “lumpectomy” which means just the removal of the mass, to a radical mastectomy (removal of the entire mammary chain and associated lymph nodes). As a general rule with this type of cancer, the best prognosis is directly related to early detection and treatment.

Unfortunately, chemotherapy hasn’t proven to be very successful in the treatment of mammary tumors in dogs - surgical removal is the primary treatment. There are no home remedies for mammary tumors in dogs.

Can mammary tumors be prevented in dogs?

Although it has been long thought that early spaying is key in the prevention of mammary tumors in dogs, there is current, ongoing research suggesting otherwise. It’s important to talk to your vet about when to spay your dog as, depending on the breed, early spaying may increase the lifetime risk for other types of cancers.

One of the best things you can do for your dog at home is to frequently feel along and under both sides of mammary chains (there should be four nipples on each side). Familiarize yourself with how the tissues feel. Your dog will no doubt love those extra belly rubs! Should you come across anything new or different, contact your vet right away.

When to Contact a Vet

If you find any sort of mass, new or unusual tissue, or even discharge from your dog’s nipples, it’s important to contact your vet right away, as early detection is the key to success in the surgical removal or treatment of mammary tumors, or any other type of mass for that matter.

Read more:

Warning Signs of Cancer in Dogs

How to Examine Your Pet at Home: A Step-By-Step Guide

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