Introduction

Bitches have, on average, ten teats, called mammary glands, five down each side.

Mammary tumours are, unfortunately, very common. About half of all the tumours we see in dogs are in the mammary gland. The equivalent in people would be breast cancer.

My bitch has a lump by one of her teats. What is it?

Not all lumps on the mammary tissue are tumours. Other diseases causing lumps include mastitis, an infection in the gland, or cysts.

Mammary tumours sometimes get bigger just after a bitch has a season. This is because they respond to a hormone called progesterone.

If you detect a lump in your dog you should seek attention from your vet, as it is important to deal with tumours promptly. Smaller tumours, less than 30mm have a better prognosis than larger tumours.

About half of mammary tumours are malignant (likely to spread around the body to the lungs, liver, bone or other places) and half are benign (unlikely to spread further). It is not possible to tell by feeling or look which will spread and which will not. To find out, a sample of the diseased area (called a biopsy) must be sent away to a specialist laboratory for microscopic examination. This is called histopathology and it can take over a week for a result to come through.

My vet has said an operation is necessary. What happens next?

The best treatment for these tumours is surgery to remove them.

On the day of the operation, it is likely that your vet will ask to perform a blood test. This is to give an indication of the overall health of your pet. It may pick up on organ dysfunction, which may or may not be related to the main tumour.

We also recommend a chest x-ray to look for any signs of spread of the tumour. Mammary tumours are sometimes quite aggressive and can metastasise, or spread, into the lungs.

If no problems are found surgery will then go ahead.

Your vet will decide whether one gland or a set of glands needs to be removed. Often it is necessary to stitch in a drain tube at the end of the operation to allow drainage of fluid from the wound. Your surgeon and nurses will explain any aftercare necessary when you collect your pet. Sometimes, if there is a lot of fluid draining from the wound, we may suggest hospitalising your bitch over night.