Mammary cancers can be either benign or malignant and are found almost exclusively in intact females that have had at least one litter or have come into heat at least once. Occasionally even very young intact females under two years of age will have tumors, but typically these can be removed with a very high success rate. Spayed females have a very low incidence of mammary cancer, and females spayed before their first litter have the lowest chance of developing the condition. Very occasionally males, usually those that have not been neutered, may also develop mammary cancer and this is usually very aggressive or malignant and the prognosis is very poor for recovery.
Mammary cancer is typically first noted as small or larger small or irregular lumps in or around the mammary glands. For both males and females there are typically five mammary glands on each side of the body, running down the chest and belly from the front legs to the front of the back legs. Both males and females will have a small nipple at approximately the center of each mammary gland, with the size and development of the mammary gland dependent on the number of litters of puppies the female has had as well a the physical attributes of the breed. Usually mammary cancer is first noted in the two sets of mammary glands closest to the hind legs of the dog. To palpate the mammary glands have the dog lie down on her back, and then gently press on the tissue around the nipple. Hard pea like or seed like bumps that are hard to the touch and do not move with the rest of the tissue are the first signs of tumors. Benign tumors tend to grow relatively slowly and stay more rounded in shape than malignant tumors that grow very rapidly and are highly irregular in shape. Occasionally tumors can become ulcerated and either bleed internally or externally, and a vet should immediately be consulted upon detection of the tumors to prevent this from happening.
The vet will want to complete a biopsy to determine what type of tumor is present. This involves a surgical procedure that takes a very small slice of tissue from the tumor for examination. If the tumor is benign it is usually surgically removed, however if the tumor is found to be malignant it will need to be removed plus other organs of the body must be checked for signs of cancer. Often the lymph nodes that are attached to the mammary system are the first places that the vet will check. The heart and lungs can also be checked for signs of tumors or cancer. Approximately 50% of all dogs with mammary cancer have successful surgical removal of malignant tumor with no reoccurrence, provided it is detected before the cancer has spread to any other organs. Chemotherapy, radiation therapy and diet and pain management are all possible treatment options in cases where the mammary cancer is inoperable.
The best way for any dog owner to prevent this disease from occurring in their pet is to have them spayed before they first come into heat. Even females that have had their first heat are still at a lower risk than those that are not spayed at all.