Breast Cancer in Dogs

A mammary tumor is a tumor originating in the mammary gland. It is a common finding in older female dogs that are not spayed (the incidence rate is one in 4 in unspayed female dogs over the age of 4), but they are found in other animals as well. The mammary glands in dogs are associated with their nipples and extend from the underside of the chest to the groin on both sides of the midline. There are many differences between mammary tumors in animals and breast cancer in humans, including tumor type, malignancy, and treatment options. Mammary tumors can be small, simple nodules or large, aggressive, metastatic growths. With early detection and prompt treatment, even some of the more serious tumors can be successfully treated. There are multiple types of mammary tumors in dogs. Approximately 50% of all mammary tumors in dogs are benign, and the other 50% are malignant. The most common benign form of canine mammary tumors is actually a mixture of several different types of cells. For a single tumor to possess more than one kind of cancerous cell is actually rare in many species. This combination cancer in the dog is called a ‘benign mixed mammary tumor’ and contains glandular and connective tissue. Other benign tumors include complex adenomas, fibroadenomas, duct papillomas, and simple adenomas. The malignant mammary tumors include: tubular adenocarcinomas, papillary adenocarcinomas, papillary cystic adenocarcinomas, solid carcinomas, anaplastic carcinomas, osteosarcomas, fibrosarcomas, and malignant mixed tumors. The 10 Early Warning Signs of Cancer ( From the American Veterinary Medical Association) ■Abnormal swellings that persist or continue to grow ■Sores that do not heal ■Weight loss ■Loss of appetite ■Bleeding or discharge from any body opening ■Offensive odor ■Difficulty eating or swallowing ■Hesitation to exercise or loss of stamina ■Persistent lameness or stiffness ■Difficulty breathing, urinating, or defecation