These are tumors found in the mammary glands (milk-secreting organs). They are the most common tumors found in female dogs. Usually appearing in middle-aged or older dogs, these tumors are sometimes cancerous. Hormonal influences are suspected causes.

The first sign noticed is usually the appearance of small lumps in mammary gland tissue. Female dogs, especially unspayed pets should have their mammary glands checked frequently by owners.

Treatment: Because mammary tumors are usually malignant, it is recommended that all mammary tumors and associated glandular tissues be removed surgically. Before surgery, a radiograph (x-ray) of the chest is taken to screen for metastasis (spreading) or malignant tumors to the lungs. An ovario-hysterectomy (spay) is often recommended to prevent development of uterine disease.