Moreover, immigrants to areas with higher levels of solar radiation have an increased rate of melanoma compared with similar individuals in their homeland. Unlike the more common skin cancers that are associated with high cumulative doses of ultraviolet light, most melanomas appear to be associated with intense, intermittent exposure, particularly during childhood and adolescence. 11,12,13,14 Epidemiologic studies have repeatedly shown an increased risk of melanoma with greater numbers of melanocytic nevi. In one study, the risk of melanoma was double in individuals with 50 to 99 small nevi compared with those with less. In addition, the presence of a solitary dysplastic nevus doubled the risk of melanoma, while having 10 or more dysplastic nevi was associated with a 12-fold elevation in risk.
Melanoma occurs more frequently in lightly pigmented individuals.
Blue or green eyes, blond, fair, or red hair, tendency to freckle, and inability to tan are all documented risk factors. Genetic linkage studies have identified a familial melanoma gene, CDKN2, on chromosome 9p21 which encodes the tumor suppressor protein p16. 16 Mutations in this gene have been documented in up to 50 percent of familial melanoma patients that link to chromosome 9p. In the United States, the ABCD checklist for detecting melanoma is often used. The criteria making up the ABCD checklist are all physical examination features.