Effects of Breast Cancer (Mammary Gland Tumors) – From the Dog’s Point of View
Dogs with breast cancer often don’t seem to know that they have it, especially during the early stages. Certain types of breast cancer, such as inflammatory carcinoma, are very aggressive and can cause the affected mammary glands to ooze, abscess and become extremely painful. But again, in most cases, the affected dogs seem to be oblivious to their condition.
Symptoms of Breast Cancer (Mammary Gland Tumors) – From the Owner’s Point of View
Many times, breast cancer is found during a routine physical examination when a dog’s owner had no idea there even was a lump in one or more of his pet’s mammary glands. However, owners of dogs with mammary tumors may notice one or more of the following signs:
- Single or multiple firm, well-circumscribed lumps, swellings, masses or nodules in the mammary gland chain (typically associated with a nipple; may or may not be ulcerated or abscessed; may be freely movable and more likely benign, or fixed to the skin or muscle and more likely malignant)
- Pain when mammary glands are palpated (physically manipulated)
- Abnormal secretions coming out of one or more nipples when they are manually expressed
- Enlarged lymph nodes (painful swellings under the armpits [axial lymph nodes] and/or in the groin region [inguinal lymph nodes]; suggests metastasis)
- Other signs may be seen if the tumors have metastasized to other areas, such as lameness with metastasis to the bone, respiratory abnormalities with metastasis to the lungs, general signs of systemic illness if the cancer has spread to multiple vital organs)
Dogs at Increased Risk
Certain breeds have been reported to have a heightened incidence of breast cancer. These include: English Springer Spaniels, Cocker Spaniels, Brittany Spaniels, English Setters, English Pointers, Boxers, Toy and Miniature Poodles, Dachshunds, German Shepherds, Dobermans, Maltese and Yorkshire Terriers. Older dogs are more susceptible to developing breast cancer than younger dogs, and males are almost never affected. Intact females – especially older ones – definitely have a greater chance of developing breast cancer than those that are spayed before their third heat cycle.
Spaying female dogs reduces their risk of developing breast cancer if done before they are around 2 years of age (before their third estrus cycle). However, spaying also increases the chance that the bitch will become incontinent, especially when she is sleeping. Approximately 20% of spayed bitches reportedly become “bed wetters” because of the loss of estrogen associated with removal of their uterus and ovaries. This condition is manageable with daily oral medications, but unfortunately is not considered to be curable. It can be an inconvenience to owners.