Melanoma is the most virulent type of skin cancer and the type most likely to be fatal. As with the other common skin cancers, melanoma can be caused by exposure to the sun, and its incidence is increasing around the world. There also appears to be a hereditary factor in some cases. Although light-skinned people are the most susceptible, melanomas are also seen in dark-skinned people. Melanomas arise in melanocytes, the melanin-containing cells of the epidermal layer of the skin. Melanin is the pigment that gives skin color and that helps to protect the skin from sun damage. In light-skinned people, melanomas appear most frequently on the trunk in men and on the arms or legs in women. In blacks melanomas appear most frequently on the hands and feet. It is unknown whether melanoma in blacks is related to sun exposure. It is recommended that people examine themselves regularly for any evidence of the characteristic changes in a mole that could raise a suspicion of melanoma. These include asymmetry of the mole, a mottled appearance (variations in color from shades of brown to a bluish tint), irregular or notched borders, and oozing or bleeding or a change in texture. Surgery performed before the melanoma has spread is the only effective treatment for melanoma.