Melanoma

Causes

The main cause of malignant melanoma is ultraviolet (UV) rays from the sun. These rays damage the skin. Melanoma occurs more frequently in people who have fair skin than in people with dark skin. Risk of developing melanoma increases with increased number of moles. The risk of developing melanoma is greatest for people who have a large number of dysplastic nevi. Dysplastic nevi is a kind of abnormal mole that are generally larger than ordinary moles and have irregular and indistinct borders. Usually they are flat but parts may be raised above the skin surface. 

Personal and family history of melanoma is also a risk factor. People who have had melanoma have a high risk of developing a new melanoma. Artificial sources of UV radiation such as sunlamps and tanning booths can also cause skin damage and increase the risk of melanoma.