Feline Mammary Tumors

Mammary tumors, as the name implies, are tumors located within the mammary glands.

These tumors usually occur in female cats, and can be either benign (non-cancerous) or malignant (cancerous).

Unfortunately, a large number of them are malignant, so any swelling or mass noted within your cat’s mammary glands should be examined by your cat's veterinarian soon after discovery.

The factors which cause these tumors to form are not fully known, however hormonal levels do appear to play a part in their formation. Females spayed at any early age (before the first heat cycle) have a much lower incidence of developing mammary tumors than those that are intact or spayed later in life. For this reason, we recommend spaying all dogs and cats not intended for breeding at an early age.

Diagnosis Of Mammary Tumors:

Diagnosis of a mammary tumor is accomplished by feeling the mass inside of the mammary gland. However, removal and biopsy of all or part of the mass will be necessary to determine whether the mass is malignant or not. (A biopsy is the process of cutting the tissue into thin slices and evaluating the cells that make up the mass.)

Before surgery can be performed on your cat, your cat's veterinarian will likely want to do a thorough examination to make certain she is able to undergo the anesthesia. This examination will likely include a physical examination as well as a complete blood screen.

Chest x-rays may also be indicated to rule out metastasis (spread) of the tumor to the lungs.

Prognosis Of Mammary Tumors:

Some of the factors which help to determine the prognosis are:

• Tumor size--Larger tumors have a worse prognosis than smaller ones.
• Evidence of spread to the lymphatic system carries a worse prognosis.
• Deeper tumors or tumor adherence to deeper tissue structures carries a worse prognosis.
• An ulcerated tumor surface carries a worse prognosis.
• A history of especially rapid growth carries a worse prognosis.
• Evidence of metastasis to the lungs visible on chest x-rays carries a worse prognosis.

Treatment Of Mammary Tumors:

Once the surgical removal of the mass has been performed and the biopsy results obtained, more specific recommendations can be made for your cat, based on her individual type of tumor and whether or not it is malignant.

If the lesion is benign, based on the biopsy results, there may be no other treatment necessary.

However, if the tumor is malignant, your veterinarian will need to evaluate whether a complete removal of the tumor has been accomplished.

In some cases, a second surgery may be necessary to remove additional tumor tissue.

In other cases, options such as chemotherapy, radiation therapy or anti-estrogen therapy may need to be explored.

Your cat's veterinarian may also advise periodic follow-up radiographs (x-rays) of your cat's chest to check for evidence of tumor presence.

Your cat's veterinarian may also advise spaying your cat (even after a tumor is located) because tumor growth, in some cases, can be stimulated by female hormones.