Martha is a 9 year old, intact (unspayed) Labrador Retriever who presented for examination of a very large skin growth that appeared to be associated with the mammary glands. The mass had slowly grown over the course of a year, and eventually Martha was having difficulty playing and running due to the position of the mass on her abdomen.

Surgical removal of the mass, along with an ovariohysterectomy (spay), was recommended. Removing the mass would serve not only to provide Martha with some relief, but also allow us to submit tissue or biopsy samples from the mass to obtain a diagnosis. A spay was recommended because mammary masses are generally hormone associated, and studies show that dogs spayed at the time of mass removal live 50% longer than dogs that are not spayed.

The biggest concern with removal of a mass this size is a sudden loss of a large volume of blood, leading to shock. Tumours or masses, whether cancerous or not, often have a very extensive blood supply. When removed, the blood contained within the tissue is taken with it, and there is some concern that there is a sudden removal of too large a volume of blood. We can prevent shock by administering IV (intravenous) fluids during surgery in order to maintain blood pressure, and in some cases may even provide a blood transfusion if the blood loss is significant and life threatening.

Martha’s mass was very well attached to the tissues on the abdomen, and there were very large blood vessels supplying the mass. In order to safely remove the mass without causing a significant amount of bleeding, blood vessels are clamped, then ligated (tied off) with suture material before they are severed. Once the tumour is removed and all of the bleeding is under control, the incision is closed in 2 layers (the subcutaneous layer and the skin layer).


Many types of mammary tumours exist, each one carrying a different prognosis for survival, and a different course of treatment. Tumours may be benign (non-cancerous) or malignant (cancerous). Martha’s biopsy results came back as a low grade mammary adenocarcinoma. Although this type of tumour is malignant, it has a low chance of metastasis (spreading to other organs and tissues in the body), and surgical removal appears to be curative. Other types of malignant or aggressive tumours may require chemotherapy following surgery in order to increase the chances of survival. The best way to prevent mammary tumours is to spay your dog prior to her first heat – dogs spayed following their second heat have a 4-7 times greater chance of developing mammary tumours later in life.

Martha has been doing great since her surgery and is able to run and play like she used to!

Other surgery photos: