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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 liver.

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 Tumors

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.


WebMD Veterinary Reference from "Dog Owner's Home Veterinary Handbook"

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