Background
Mammary tumors:

Are growths involving mammary glands (breast tissue) of dogs and cats.

Typically occur in females, rarely occur in males.

Occur more frequently in dogs than cats.

Can often be prevented by spaying female dogs early in life.

Anatomy

Dogs normally have 5 pairs of mammary glands.

Cats normally have 4 pairs of mammary glands.

The glands are connected in a “chain” on either side of the belly.

The Disease

As with all cancer, no one knows why mammary tumors occur.

In dogs, 50% of mammary tumors are benign; 50% are malignant.

In cats, 90% of mammary tumors are malignant; only 10% are benign.

Malignant mammary tumors often spread to other glands, then to associated lymph nodes, then to the lung tissue.

In cats, the tumors can spread down a chain as well as across to the opposite chain.

The Diagnosis

Most mammary tumors are found on routine exam or while being petted.

Mammary tumors must be removed and biopsied in order to determine whether they are benign or malignant.

Bloodwork and Chest Radiographs are often part of the pre-surgical tests.

The Surgery

Requires general anesthesia and typically an overnight hospital stay.

Surgery typically involves removal of the tumor tissue only.

Depending on the size, number and location of tumors, the entire gland, multiple glands and/or the associated lymph node may be removed.

Aftercare

Antibiotics, pain medication and restricted activity are prescribed post-op.

Follow-up Treatment

No additional treatment is required for benign tumors.

Chemotherapy, radiation therapy or additional surgery may be recommended for malignant tumors.