[Solar radiation and melanomas--is there any doubt about the connection?]

Arguments for and against there being a connection between exposure to solar radiation and cutaneous, malignant melanoma are reviewed. Recent experiments with animals and epidemiological observations provide relatively strong arguments that solar radiation causes cutaneous, malignant melanoma. Furthermore, epidemiological data from Norway and Australia support the assumption that UVA-radiation plays a significant role in melanoma induction; this is in agreement with data from experiments with Xiphophorus and Monodelphis domestica. A new hypothesis for melanoma induction is presented: Radiation absorbed by melanin in melanocytes generates free radicals that may activate the carcinogenic process. Radicals produced by light absorption in melanin in the upper layers of the epidermis are not able to diffuse as far down as to the melanocytes. Thus, this melanin may be protective, while that in the melanocytes may be a photocarcinogen. Findings that support this hypothesis are discussed.