Canine melanoma, one of the five most commonly diagnosed cancers, can develop in many places on a dog’s body. The behavior of the tumor depends on its location.
What is it? Canine melanoma develops in pigment cells on the skin (where it’s usually benign, unlike human melanoma), in the mouth, in the nail bed (toenail), or in the pads of the foot, or in the eye. While human melanomas are generally the result of too much sun, it does not appear to be the case in dogs. White dogs are rarely affected by melanoma; It is more common in dogs with dark coats and darkly pigmented skin. Oral melanoma (OMM) is the most common form and is often discovered during a routine exam or by the owner. It can appear on a dog’s gums, lips, tongue, or hard roof of the mouth.
Signs and symptoms.
Melanoma usually (but not always) shows up as a dark, raised mass on the skin or in the mouth. While a dog may not show symptoms early on, signs include drooling, bad breath, bleeding, and sometimes eating disorders. The toenail or foot pad may swell, the nail may come off, or the dog may be lame. Melanomas in the mouth or in the nail bed are the most aggressive.
How is it diagnosed?
Melanomas are diagnosed by fine-needle aspiration (a quick, well-tolerated and inexpensive way for the veterinarian to take the mass) and / or biopsy. To refine the diagnosis and stage the cancer, the vet will take blood and urine samples, examine nearby lymph nodes, and X-ray or perform a CT scan of the breast.
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How is it treated?
Regardless of where it appears, surgery to remove the primary tumor is the first and best treatment, followed by radiation or immunotherapy to slow its spread. If the location of the melanoma rules out surgery, radiation or immunotherapy alone may be used. Because melanoma tends to be unresponsive, chemotherapy is rarely part of the treatment protocol.
Dogs that have had oral surgery, including removal of part of the upper or lower jawbone, generally have good functional results, adapt to the new shape of their jaws, and learn how to eat as early as three days after surgery.
Radiation usually involves three to six treatments performed daily or weekly. Doses higher than standard seem to give a better response. Immunotherapy uses the dog’s immune system to fight cancer. Oncept, a DNA vaccine, has shown promising results against oral melanoma. According to the literature, “Dogs with stage II and III OMM treated with Oncept after surgical resection (with or without radiation therapy) had longer median survival times than dogs in the control group.” The vaccine, which is made from DNA that is responsible for a melanocyte protein encoded in the human gene causes the dog’s immune system to attack its own version of the same protein. It can also affect the dog’s skin cells, which sometimes causes the dog to have more gray fur after treatment.
Unfortunately, if detected, melanoma is often metastatic. In most cases, after a melanoma is surgically removed, metastatic tumors appear in the lungs after a few months. OMM is spreading particularly quickly.
Are Certain Races Predisposed?
While any dog can develop melanoma, the following breeds are considered predisposed: Cocker Spaniels, Chow Chows, Scottish Terriers, Black Labs, Black Poodles, Golden Retrievers, Dachshunds, Dobermans, and Standard and Miniature Schnauzers.