On the causes of melanomas.

A large number of factors have been identified which seem to predispose an individual to develop melanoma. Black-skinned individuals rarely have malanomas, but this variety of tumors is common in red-haired or blond subjects. The incidence of melanoma is particularly high if such fair-skinned subjects are exposed for long perods of time to intense sunlight. Nevi, congenital or acquired, can degenerate into melanomas. In some families, many of the family members develop multiple nevi that are unusually large and red in color. All of these appear to degenerate into melanomas with time. Nature has provided other examples of genetic factors which induce melanomas, i.e., the melanomas which form in the platyfish and Sinclair miniature swine.