Oz: Mammary cancer a growing problem in female dogs

Breast cancer has been one of the hottest topics drawing people’s attention and awareness in the last few years.

Breast cancer has been one of the hottest topics drawing people’s attention and awareness in the last few years.

There are numerous fundraising campaigns to recruit financial help in improving and further developing the research on human breast cancer diagnosis, treatment and prevention.

Women are not the only target of this nasty cancer, pets very often suffer from this type of cancer as well.

In fact, according to veterinary literature, breast cancer in female dogs is three times more common than in women.

Mammary cancer types and biologic behaviour differs between dogs and cats.

The exact mechanism and the cause of mammary cancer is still unknown. However, it is known that the female hormones (estrogen and progesterone) play a role in its development.

Mammary tumors in dogs are most frequent in intact female dogs, they are extremely rare in male dogs.

Due to the cancer relation to hormones it is very important that new dog owners be aware that they are able to be proactive and most likely prevent the cancer occurrence in the female dog just by simply spaying her at an early age.

Spaying a female dog before the first estrus cycle reduces the risk of mammary neoplasia to 0.5 per cent of the risk in intact female dogs, this is a very low risk. If the procedure is done after one estrus cycle, it reduces the risk to eight per cent.

Female dogs spayed after maturity (had two or more estrus cycles) have generally been considered to have the same risk as intact bitches. Spaying the dog at maturity still carries other medical benefits, but unfortunately does not prevent mammary cancer.

In cats it is a different story. Early spaying, before the first menstrual cycle, does reduce the chances for mammary cancer development but the degree of protection is less precisely documented than for dogs.

Not all mammary tumors in dogs are cancerous. In fact, only 45 to 50 per cent of mammary tumors are cancerous in dogs. In cats, however, about 90 per cent of mammary tumors are cancerous.

A mammary tumor is usually suspected on detection of a mass during physical examination. Grossly, the tumors appear as single or multiple nodules in one or more glands. The tumor appearance is usually lobulated, gray-tan in colour, firm to the touch, and often with fluid-filled cysts.

Once the tumor has been found, a pathological examination is required in order to characterize its nature.

This is done by sampling the tissue either by fine needle aspiration—an easy procedure that is usually done within several minutes, and commonly does not require sedation/anesthesia.

Fine needle aspiration cannot always guarantee reliable results.

A more accurate method for obtaining the true nature of the tumor is by acquiring a true sample of the tumor tissue, a surgical procedure that requires anesthesia.

Once the tumor was diagnosed as cancerous, other tests such as lymph nodes sampling and chest x-rays are recommended in order to assess the tumor spread.

The primary treatment for any mammary tumor is surgical.

The surgical options include the removal of the tumor only (lumpectomy), removal of the affected mammary gland (mastectomy) or removal of the entire mammary chain (radical mastectomy).

Chemotherapy is also available but is not always successful in helping prolonging the pet’s life.

The earlier the tumor is found and diagnosed the better the chances for treatment and spread


If you suspect mammary tumor in your pet, take it to be checked by your vet as soon as possible.

If you just adopted a kitten or a puppy and you are not interested in breeding it, don’t delay the spaying.

Beyond spaying, keeping your pet fit, in good body condition and eating a healthy diet. That will also play a role in mammary tumor prevention.

It has been demonstrated that the consumption of red meat, obesity at one year of age, and obesity a year prior to the tumor diagnosis are associated with an increased risk of mammary gland tumors in both intact or spayed dogs.

You are able to be proactive and help with the prevention of mammary tumor in your pet.

Talk to your veterinarian for more information on mammary tumors.

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