Melanomas originate in the cells called melanocytes which produce a pigment called melanin. A malignant tumour is known as a malignant melanoma or melanosarcoma. A benign tumour is known as melanocytoma. They are most commonly found on the skin, the mouth and the toe nail bed. Melanomas found on the skin are generally benign.
Melanomas found in the mouth and toe nail bed are normally malignant. When found in the mouth the most common signs iare swelling of the mouth, excessive drooling, weight loss and the inability to eat. Oral melanomas are locally aggressive and have a high rate of spread to the lymph nodes and kidneys. In the toe nail bed you may see swelling of the toe similar to an infection, loss of nail and limping on the leg. Tumours that grow from the toe nail bed are more aggressive and about a half of them will have spread throughout the body.
Surgery is usually the best treatment option and for many dogs when the tumour is on the skin, it can be curative. After removal they should be sent to the laboratory to determine if they have been completely removed. Due to the likelihood of spread with melanomas found in the mouth and toe, your oncologist will recommend a number of different tests to determine the spread. An individual treatment plan can then be done for your dog to give the best outcome. Tests may include, blood tests, xrays, ultrasound and CT/MRI.
Dogs often respond well to high doses of radiation or local injections of chemotherapy when the tumour is inoperable or when aggressive surgery was unable to get clean margins. Chemotherapy is also used to treat the spread to other areas of the body. A vaccine has also become available which can give quality of life for much longer. As with any canine cancer, your oncologist can give you the best advice with the primary goal being to give a good quality of life for as long as possible.
**Accuracy checked 27 September 2013,
Dr Ken Wyatt BSc BVMS FANZCVS,
Registered Specialist in Veterinary Oncology,
Perth Veterinary Oncology
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