The prognosis for a dog diagnosed with melanoma depends on many factors, but the location of the tumor is primary. Oral melanoma is particularly aggressive, rapidly metastasizing to various organs. Melanomas on the skin are often benign. Those found in the foot, another common location, have a 50 percent chance of malignancy.
Canine melanoma most often occurs in the mouth, with the foot pad and nail bed another frequent location. According to Michigan Veterinary Specialists, oral melanoma is the most common oral tumor in canines, with a metastasizing rate of 80 percent. Tumors appearing near or in the eyes are often benign, but malignancy is a possibility.
Although any dog can develop canine melanoma, some breeds appear predisposed to the disease. These include the chow, miniature poodle, Gordon setter, German shepherd, boxer, cocker spaniel, Scottish terrier, German short-haired pointer, golden retriever, Weimaraner and the Boston terrier. Oral melanomas occur more frequently in senior male dogs.
Dogs afflicted with oral melanoma experience mouth swelling, bad breath, bleeding, excessive salivation, difficulty eating, tooth loss, lack of appetite and weight loss. If the cancer spreads into the lymph nodes, the lower jaw might swell. Since oral cancer often spreads to the lungs, dogs might start coughing and appear lethargic. The initial symptoms of cutaneous melanoma, appearing in the nail bed and foot pad, might be lameness or loose toenails. Eye tumors appear as masses in the iris or near the eye.
Your vet must surgically remove the tumor, also taking out a large margin of tissue. Surgery is often followed by radiation and chemotherapy. If your dog suffers from foot pad or nail bed melanoma, leg amputation might prevent metastasis. According to the Animal Cancer Center of Colorado State University Veterinary Teaching Hospital, dogs diagnosed with malignant melanoma live an average of six to eight months if treated with surgery alone. If the tumors are especially large or have spread to the lymph nodes, affected canines probably will succumb before that.
In 2010, the animal health company Merial received U.S. Department of Agriculture approval for its canine melanoma vaccine, marketed under the name Oncept. According to Merial, this vaccine was developed jointly with Memorial Sloan-Kettering Cancer Center, one of the world's premier facilities for treating human patients. The vaccine does not prevent melanoma, but appears to significantly lengthen the lifespans of dogs afflicted with the disease. Oncept is delivered transdermally, or via a patch, rather than through a needle.