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Breast Cancer Awareness: Mammary Carcinoma in a Dog

Yesterday evening I was working closing shift. I had a walk-in coughing dog, whom I had seen previously for a corneal ulcer. While I was doing my physical exam on this dog, our technician came in to say we had a dog come in that wasn’t breathing well.

I left a coughing dog and went to a dyspneic dog and did a quick assessment of the scene and of the patient, getting a brief history from the owner, and then I strongly advised humane euthanasia. I won’t go into details about everything that happened, because I am still dealing with the trauma myself. My team pulled together and we managed in the end. But I knew I wasn’t going to ‘save’ this patient.

This case is a 7-year-old female intact German shepherd cross who I suspected was suffering from SIRS due to decompensation from mammary carcinoma. I recall learning about shock in school. This dog was experiencing this. Due to my suspicion of the disease and high likelihood of malignancy of the tumours, euthanasia was the best treatment for this patient.

While many would like to know more details, so that they can learn through the case presentation, the real reason I wanted to talk about this case is that this disease is preventable by an ovariectomy, or spay procedure. Similar to some breast cancer in women, the majority of these cases of cancer are caused by the females’ hormone estrogen.

The veterinarian has an obligation to educate owners of female puppies. The discussion of the spay procedure needs to occur when the owner comes in for the puppy shots. We also need to follow-up with these owners to recommend spay if they are not planning on breeding them.

The stats out there for prevention of mammary carcinoma for dogs is that if you spay the dog prior to its first heat, they have close to zero percent likelihood of developing breast cancer. If the spay occurs after the first heat, but before the second, the risk is roughly 7%. Once they are allowed to experience several heat cycles (without pregnancy) about 1 in 4 intact females develop mammary carcinoma. Since it is the most common tumour in an intact female dog, as soon as the owner told me she was not spayed, I knew what I was dealing with.

I use a few resources online for client education, especially with the internet available. The Veterinary Partner is a link I am commonly recommending for information that is written in layman’s terms, so that the science is understood. The majority of female dogs are spayed because owners do not want to deal with a female dog in heat and unwanted pregnancies. Some of them I convince to spay to reduce the incidence of pyometra, or infection in the uterus. Outside of breeding bitches, the intact female dog is rare, but cost constraints for the surgery exist. Fortunately, we have local humane societies that we can refer owners to so that they can still get this procedure performed, without having to spend two times their monthly rent. However and wherever it is performed, it is in the best interest of the non-breeding dog.

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