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Dr. Marty Greer

October is Breast Cancer Awareness Month. Every October, we are reminded to spread the word about breast cancer prevention and early detection. That awareness extends to our dogs as well.

How does hearing the words “she’s got breast cancer” affect you? Does it bring tears to your eyes? Start a knot in the pit of your stomach? Unleash anger at being cheated? Make you want a second opinion?

The Diagnosis  

Plenty of people know someone who has been affected by this dreaded diagnosis. Maybe it’s you, or perhaps someone you love, like a wife, sister, girlfriend, mother, friend, or co-workerWe know it is a life-changing experience, bringing with it the possibilities of pain, surgery, chemotherapy, radiation, and fear of a shortened life expectancy.  

For many women, advances in early detection and medical therapy have fortunately made breast cancer a story of survival instead of a death sentence. Sadly, however, some are diagnosed too late, or with a very aggressive form of the disease, some cannot afford proper medical care, and some even deny themselves the care that they need. Those who are blessed with great diagnostics and treatment largely owe their successes to the incredible research that led to this improved prognosis and outcome. 

The increasing amount of success stories over breast cancer in humans is due in part to the diseases’ similarity to mammary tumors in dogs. Dogs have served as research models for the disease in humans, and many advancements in human medicine are directly linked to the information discovered by research on the disease in dogs. Sadly, our dogs have not benefitted from cancer research as much as humans have. 

In human medicine, there are two keys to survival – early detection and successful treatment. Self-breast examinations and mammograms have been credited with changing survival through early detection, and many organizations have put their resources into educating us about the importance of these two important detection tools. New diagnostic tools are on the horizon for humans, but of course, mammograms are not available for our dogs, as they rely on us to detect their lumps and to seek appropriate therapy for cancer treatment 


Unfortunately, breast cancer treatment in humans and in dogs is vastly different. Despite the similarities between the human and canine disorders, there are no widely accepted successful chemotherapy and radiation therapy programs available for dogs, and surgical excision is the only treatment option widely available for dogs at this time.

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In contrast to humans, mammary tumors in dogs are nearly 100% preventable if owners would take one simple step – to spay female dogs prior to age 2 or younger. It’s common knowledge that spaying prevents heat cycles and pregnancy, but veterinarians have not always done as well to educate clients that spaying under the age of 2 prevents most mammary tumors, and that spaying before the first heat cycle protects nearly all dogs. 

In the veterinary profession, we have also not educated our clients of the risks of spaying our female dogs. While it is true that spaying prevents pregnancy, mammary tumors, and pyometras, there is research that supports increased risk of other disorders thought to be related to removing the hormonal influence of the ovaries. There is an increased risk of urinary incontinence and associated urinary tract infections, osteosarcoma, hemangiosarcoma, and hypothyroidism.

Each of these disorders has an associated health risk ranging from mild to severe, affecting quality and length of life, as well as financial cost to the owner. Even when dogs with mammary tumors were included in the study, however, they still achieved greater longevity than their spayed female counterparts.  

More information on the scientific literature surrounding spaying and canine health can be found here:

Individualized Veterinary Care

These studies show that the decision to spay, and when to spay an individual dog, cannot be made without balancing the risks and benefits of the procedure.  

As a group, veterinarians and animal control organizations have encouraged spaying, sometimes at a very early age, with the only goal being population control. We have overlooked the importance of individual dog health, as well as the health benefits of leaving our female dogs intact. Instead, we have allowed public policy for the greater good of dog population control to dictate decisions about spaying individual dogs.   

Every dog should be treated as an individual, and there is not a one-size-fits-all way to approach this decision. More research needs to be done to aid in determining the optimal time for a spay. 

For the dogs who are not spayed at this early age, due to their inclusion in a breeding program or for other health benefits, early detection is still key in creating a favorable outcome for the patient and her family. Early detection in the dog is simple and requires only a monthly examination by the owner, and biannual examinations on palpation by her veterinarian. For dogs groomed frequently, professional groomers may be enlisted in this hands-on approach as well. This simple “Pink Paw” program will allow for early detection for nearly all mammary tumors. When detected early, surgical removal will often lead to a cure.  

Of course, for our dogs as for us, a healthy lifestyle with an appropriate diet, exercise, good weight management, preventive veterinary care, and the fortune of good genetics will allow for maximum longevity.  

Should We Call It “Breast Cancer?” 

The same disorder we see in women and call “breast cancer” is called “mammary tumor” in dogs. This terminology may demotivate owners to respond to this as a serious health threat to their dog. Although an accurate description, “mammary tumor” is too bland of a term to use when a call to action is the best response.  

We need to think of this malady in dogs as we do in women – a cancer that requires prompt surgical treatment. Since surgery is our only real option for treatment of “breast cancer” in the dog at this time, owners and veterinarians alike should opt for wide surgical excision of any suspect masses as soon as possible to improve long-term survival of the affected patient. The only exception to this is in the rare case when inflammatory mammary carcinoma is suspected; in this case, surgical excision is not an appropriate treatment.

Taking a “let’s watch it and see what it does” approach to a lump is likely to allow a treatable disorder to rage out of control, and become a life-threatening disorder. Each heat cycle she has will likely lead to an increase in the size of the breast tumor, so spaying at this time is likely to help prevent the continued risks of mammary cancer in dogs who are predisposed to recurrence.

There is a known strong correlation between the size of the dog, the size of the tumor, and the malignancy rate – overall, 50% of breast cancer in dogs is malignant. As in women, early detection and treatment leads to a much better prognosis and long-term survival rate.   

The Future 

As we know more about the prevention, early diagnosis, and treatment of breast cancerwe as well as our dogs can look forward to a long and healthy life free of this devastating disorder. 

Marty Greer, DVM, JD, has run the Veterinary Village Small Animal Clinic in Wisconsin since 1982. She is an expert in canine reproduction, is author of Canine Reproduction and Neonatology and a frequent lecturer on the subject. Dr. Greer also studied law at Marquette University and is a partner in Animal Legal Resources, LLC and is a board member of the National Animal Interest Alliance, Director of Veterinary Services of Revival Animal Health, and President of the Society of Veterinary Medical Ethics.
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