Melanoma is a form of cancer in which the pigment-producing cells of the skin (dogs with pigmented dark skin) known as melanocytes multiply in an erratic fashion eventually invading the tissues that surround them. As a group, melanomas can be either benign or malignant and this tumor may grow rapidly, ulcerate, or bleed. In general, skin melanomas tend to be benign, and those in the mouth, toes, or eyes tend to be malignant melanomas. Melanomas can occur in areas of haired skin, where they usually form small, dark (brown to black) lumps, but can also appear as large, flat, wrinkled masses. In dogs mouth, toes of the paw or behind the eye is where Melanomas can usually occur. These dog breeds are observed to be more at risk with Melanomas: Airedales, Chow Chow, Boston Terrier, Irish Setter, Cocker Spaniel, Boxer, Miniature Schnauzer, Doberman, Chihuahua, Scotish Terrier, Golden Retriever and Springer Spaniel. Approximately 25% of dogs diagnosed with oral melanoma will survive for one year; 75% will not survive even this long.
Benign cutaneous melanomas of dogs are usually seen as round, firm, raised, darkly pigmented masses from one-quarter to 2 inches in diameter. They occur most often on the head, digits or back. Clinical signs of malignant melanomas in the mouths of dogs and cats include lack of appetite, drooling, bleeding in mouth, facial swelling, Halitosis or bad breath, or difficulty eating. A lesion with irregular borders and variable colors. The lesion may be brown or black and it may also have shades of red, white or blue. Early recognition of melanomas can lead to more successful attempts at removal and identification of the grade or stage of cancer. The risk of metastasis for benign forms of melanoma is not very high but these can be locally invasive. Malignant melanomas can metastasize (spread) to any area of the body especially the lymph nodes and lungs and present very challenging and dangerous prospects for the dog. Cats seem much less susceptible to melanoma tumors than dogs. Presence of malignant melanoma may be first discovered in the lungs where diffuse pulmonary infiltration of tumors will be displayed throughout the lung tissue on a radiograph (x-ray). Lymph node swelling or enlargement may be a clinical sign of malignant spread of a melanoma. Some melanomas do not display the characteristic darkly pigmented color of most melanomas. The pigment called melanin is a hallmark of these tumors and usually is present in large amounts in melanomas.
Primary treatment for the melanoma in dog and cats is surgical removal of the lump. Melanomas on a pet's digit usually require amputation of the toe. A biopsy of the mass is needed to grade the tumor, ie, to determine its aggressiveness. Veterinarian may also recommend blood work, x-rays, ultrasound, and examination of lymph nodes to help determine a prognosis. Other treatments are chemotherapy, radiation therapy, or immunotherapy may be recommended to cure this tumor. If the melanoma has arisen from the oral cavity and has invaded the jaw, your veterinarian may recommend that part of the jaw bone be removed as well. Radiation to promote shrinkage of the tumor. Combination chemotherapy, including dacarbazine, has helped some patients. Commonly used drugs include carboplatin or cisplatin while a new vaccine called Canine Melanoma Vaccine has been given a conditional license for the treatment of stage II or stage III oral melanomas in dogs. The future does hold promise that genetic therapies directed at stimulating the dog's own immune system to attack and destroy tumor cells may be developed. Aggressive and radical surgery greatly increases survival times and decreases reoccurrence rates.