The photobiology of melanocytes modulates the impact of UVA on sunlight-induced melanoma.

Ultraviolet radiation is responsible for melanoma. In this review, we address the role of the different UV spectra in melanoma. The data suggest that only UVB is capable of initiating melanoma, and that both UVA and UVB are involved in the progression of the disease. The etiology of sunlight-induced melanoma may be different for chronically-exposed tumors and for those located on body surfaces with considerably less exposure. Solar signature mutations are most likely associated with the progression of chronically-exposed tumors. The unique relationship between UVA and melanocytes, and the role of melanin in photocarcinogenesis is discussed. The current state of knowledge strongly indicates that UVA, regardless of its source, is involved in melanoma and should be avoided to deter progression of incipient tumors.