Number and size of nevi are influenced by different sun exposure components: Implications for the etiology of cutaneous melanoma (Belgium, Germany, France, Italy)

Objective: The solar wavelength involved in melanoma occurrence remains unknown. Sunburns and latitude gradient are indicators of greater exposure to the ultraviolet B radiation. We examined the associations between the components of holiday sun exposure with numbers of small (2-4.9 mm) and large nevi (≥5 mm) in young children. Methods: Information about each holiday period from birth to interview was recorded from parents of 628 6-7-year-old children in four European countries. Sun exposure was characterized using four different components: cumulative duration of holidays, number of holiday periods, sunburn episodes and latitude gradient between habitual living place and holiday places. Results: Individual susceptibility to sunlight, cumulative duration and number of holiday periods were moderately associated with increasing number of small but not of large nevi. The number of small nevi together with sunburn history and latitude gradient were strong predictors of large nevi number. In contrast, sunburn history and latitude gradient were not associated with small nevi. Conclusions: Exposure to high doses of ultraviolet B radiation would be implicated in the formation of large nevi, while solar radiation other than the ultraviolet B could be implicated in the development of small nevi in children. Given that numbers of large nevi are strong predictors of melanoma in children and adolescents, these results agree with the hypothesis that high ultraviolet B doses are needed for melanoma occurrence, but probably not for nevi formation.