Melanomas, Squamous Cell Carcinomas, and Mast Cell Tumors in Dogs
Melanomas arise from melanin-producing cells in the skin. They are more
common in Scottish Terriers, Boston Terriers, and Cocker Spaniels. These brown
or black nodules are found on darkly pigmented areas of skin, particularly on
the eyelids. Rarely, you will find an unpigmented melanoma. They also occur on the lips, in the mouth, on
the trunk and limbs, and in the nail beds.
Melanomas on the skin are usually benign; those in the mouth are highly
malignant. About 50 percent of nail bed melanomas are malignant and
metastasize. Metastases occur in the regional lymph nodes, lungs, and
Treatment: The melanoma must be removed surgically, along with a margin of
normal tissue. Recurrence is common and difficult to treat. The outlook is
extremely poor for melanomas in the mouth.
Perianal growths are usually benign cancers that appear around the rectum,
especially in unneutered male dogs. Rarely, these will be malignant perianal
adenocarcinomas. Siberian Huskies are predisposed to this type.
Anal sac gland tumors are a separate entity. These tumors are often
aggressive and malignant. They arise from the anal glands on either side of the
rectum and often metastasize quickly. These cancers are also associated with an
increase in calcium in the blood.
Treatment: Neutering and/or surgical removal may be curative for perianal
growths. Multimodal therapy is the best way to fight anal sac gland cancer:
surgery, radiation, and chemotherapy.