can dogs get breast cancer

Can Dogs Get Breast Cancer?

Nowadays, due to improved diet, better veterinary care, and vaccinations, our canines are living longer than ever. As with humans, this means that they can fall victim to a greater range of medical conditions as their bodies age. Cancer is one of these illnesses, and in this article, we’ll be looking specifically at what we would call ‘breast cancer’ in humans.

We don’t usually refer to the term ‘breasts’ when we’re talking about dogs; instead, the term more usually used is ‘mammary glands’. Instead of two breasts, a dog has two rows of five mammary glands running down the chest to the lower abdominal area. Externally, these display as nipples; the mammary glands below the skin’s surface produce the milk that feeds her newborn puppies.

That’s not to say that male dogs don’t have mammary glands, nor that they won’t contract breast cancer. Read on to find out more detail about breast cancer in dogs, its treatment, and the prognosis if your dog is diagnosed with this condition.

breast cancer in dogs

What’s the Likelihood of My Dog Being Diagnosed With Mammary Gland Tumors?

Female dogs are more likely to contract mammary gland tumors than male dogs. The incidence of breast cancer in female, unspayed dogs over the age of four years is around 25%. But although rare, male dogs can still suffer from the condition. Unfortunately, it’s much more likely to be serious in males, as the disease will spread aggressively, reducing the chances of effective treatment.

What Are the Symptoms of Mammary Gland Tumors in Dogs?

When you’re petting your dog, you may notice lumps or bumps in the area around the mammary glands or by the lymph nodes. They may be smooth or irregular to the touch. The lumps may be small but will show signs of growth, sometimes aggressively so, if left unchecked.

It’s important to take routine care of your dog, grooming, stroking and petting them regularly, as this is an excellent opportunity for you to spot new growths.

In more detail, symptoms you might observe include:

  • Either single or multiple lumps located within the mammary glands, particularly around one or more of the nipples.
  • Bleeding or discharge from the nipples.
  • The lumps will usually be slow to grow.
  • The surface of the skin may look ulcerated, inflamed, infected or may experience a thinning of tissue.
  • Benign masses may move freely under the surface when palpated with the fingers.
  • Malignant masses may be difficult to move when manipulated with the fingers because they are fixed to the body wall or skin.

Whatever symptoms you observe, it’s important not to panic, as there is around a 50%  chance of any lumps you find being benign. Other conditions could also result in similar symptoms, so a cancer diagnosis is not inevitable. But do seek your vet’s advice as soon as possible. The condition can only be treated correctly once it’s been identified.

How is Cancer in Dogs Diagnosed?

  • Your vet will usually take blood and urine samples.
  • Your dog will be x-rayed along its chest and abdomen, to check that all the tumors have been caught and none have spread further afield (‘metastasized’).
  • The vet will take samples of the mass and of the lymph nodes by inserting a fine needle into the affected areas. Alternatively, a biopsy will be necessary, where surgery is needed to cut into the mass and take a larger sample. In this case, an anesthetic or sedation may be needed. Laboratory analysis will determine whether the lumps are malignant or benign.

How is Cancer in Dogs Treated?

Again, just as with humans, the sooner the condition is spotted and diagnosed, the better the chances of recovery and survival.

The main course of action is usually surgery to remove the tumor(s). Depending on the type of tumor, the rate of growth and spread, and the age of your dog, the vet may just remove the lump itself. Alternatively, he or she may decide to remove the tumor, the surrounding tissue, mammary glands and lymph nodes. If it’s not achievable to remove the entire tumor, as much as possible will be taken out.

Surgery has a good chance of success, and the good news is that dogs tend to recover pretty quickly from the procedure. If your dog has been otherwise fit and healthy, you can expect her to be back to her normal self within about a fortnight. However, she’ll still need frequent follow-up appointments with her vet or oncologist, though.

Chemotherapy and radiotherapy have not been commonly used as treatments for mammary gland tumors in dogs to date, although new technologies and medical progress means that these routes are becoming more possible. Your vet will advise on whether either treatment is appropriate, often after consulting with an oncology specialist.

Chemotherapy involves the use of systemic drugs to destroy any remaining cancer cells. Radiotherapy involves administering targeted radiation to tumors that can’t be completely removed or to tumors that haven’t spread to other parts of the body. Both courses of treatment will also attack healthy cells and may cause your dog to feel under the weather, with side effects including diarrhea, vomiting, reduced appetite, hair loss, and/or a drop in the white blood cell count (making them more prone to other infections).

To prevent recurrence of cancer, your dog may also be spayed if this hasn’t already been done. There’s currently little medical evidence to prove that spaying unneutered dogs, especially older females, will prevent cancer from returning, but some vets may recommend this as an option.

breast cancer in canines

What Can Affect the Type of Treatment Your Dog Receives?

When deciding how to address the problem, your vet will take into account the age of your dog and any other health issues she is currently suffering from. Other important factors include the number of tumors and where they’re located. Generally, the deeper within the tissue the tumor is located, the harder it is to remove and the greater the possibility of cancer spreading. The biopsy samples, x-rays, and urine and bloodwork your vet carry out will all be analyzed to determine the type of tumor and the best form of treatment for your dog specifically.

What’s the Prognosis for My Dog Once It’s Been Diagnosed?

Survival rates depend on the type, the severity and the spread of the tumor(s). The prognosis for dogs who’ve had benign tumors is excellent. And if a malignant tumor is caught and removed in its entirety early, before it’s grown to around 5cm in diameter, there’s a good chance that your dog will stay in remission for a long time to come.

But if the carcinoma has spread to the lymph nodes or metastasized throughout the body, it’s likely that unfortunately, your dog’s lifespan will be limited. Your vet will discuss this with you in full detail before any decisions are made on treatment.

How Can I Prevent My Dog From Developing Breast Cancer in the First Place?

There’s no way to completely eradicate the possibility of breast cancer in dogs, as the causes of this illness are likely to be hereditary or due to hormones. But there are ways you can look after your pet’s overall health that will help minimize her chances of contracting this illness. These will also generally make sure she is fit and healthy in other ways and able to fight off a range of diseases and infections.

If you own a puppy or young dog, having her spayed before she goes into heat for the first time will greatly reduce her chances of developing mammary tumors. If you’ve missed this opportunity, even spaying her before she reaches 2.5 years of age will decrease the likelihood of the condition developing. After that, though, the benefits of spaying as a prevention against cancer aren’t proven.

Keep your dog’s weight within a normal range for her breed. There are strong links between being overweight and obese and the incidence of many types of cancer. Ensuring she’s as sleek and lean as she should also improve your chances of spotting potentially dangerous health conditions early. If she’s covered in rolls of fat, it’s not as easy to detect the lumps ad bumps associated with cancerous growths.

Just as humans are advised to carry out regular examinations on their own bodies to check for growths and lumps, so you should do the same for your dog. As noted, identifying problems at an early stage improves the chances of successful treatment enormously. You may be able to catch the growths before they turn malignant or spread to other parts of the body.

When you’re stroking or grooming her, run your hands under her front armpits, around her belly and down towards her rear armpits and groin area. Any new spot or lump should be pointed out to your vet as soon as possible – it’s not worth waiting to see if it grows or if further bumps and lumps develop.

Are Some Types of Dog More Likely Than Others to Contract Mammary Gland Tumors?

As already mentioned, gender is certainly a factor: significantly more female dogs than male ones are diagnosed with this condition. But that’s not to say males never contract breast cancer, so do check frequently and look out for the symptoms above.

Genetics also plays a part, with some breeds more likely than others to be affected by malignant breast tumors. These include:

End on a Positive…

Remember that finding a lump on your dog’s body – or even being told that she or he has cancer – is not a death sentence. Treatments are improving all the time and canines’ chances of surviving cancer are too. Don’t bury your head in the sand and avoid the issue: get your pet checked by the vet as soon as possible and above all, stay positive throughout. Your dog will pick up on your mood, and while not necessarily scientific, positivity can really help with recovery.


  1. Dr. McEntee, Mammary Tumors, Cornell University College of Veterinary Medicine
  2. Cancer in Pets, American Veterinary Medical Association
  3. Canine Mammary Tumors, College of Veterinary Medicine


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