Malignant melanoma on the thigh of a 59 year old female patient. Melanoma is a form of skin cancer that arises from melanocytes, the cells that produce melanin, the pigment that gives skin its colour. Symptoms of melanoma include a change to a mole, freckle or normal patch of skin. The main cause of melanoma is exposure to ultraviolet radiation in sunlight. It is an aggressive cancer that often spreads (metastasises) to other parts of the body. Treatment is with surgical excision of the melanoma. This melanoma measures 0.36 millimetres on the Breslow Index (depth from skin surface).