ULTRAVIOLET EXPOSURE AND THE DEVELOPMENT OF BANAL AND ATYPICAL NEVI -A CROSS-SECTIONAL STUDY ON CURACAO AND IN THE NETHERLANDS

The atypical naevus is both a risk factor for and a precursor lesion o f melanoma. sunlight is known to be an important aetiological factor f or melanoma. Whether solar exposure is also involved in the initiation of (atypical) naevi is an issue of current interest. We performed a c ross-sectional study among 270 inhabitants in the cloudy Netherlands a nd 282 white Dutch immigrants of the tropical island Curacao to invest igate whether solar exposure plays a role in the development of atypic al naevi. All participants were interviewed and underwent total skin e xamination; banal melanocytic naevi and atypical naevi were counted. T here was no significant difference in the mean number of melanocytic n aevi greater than or equal to 2 mm or greater than or equal to 5 mm be tween Curacao and the Netherlands. Furthermore, there was no significa nt difference in the mean crude and age standardized prevalence of aty pical naevi between the Netherlands and Curacao. In both groups indivi duals with atypical naevi had significantly more total naevi. Concerni ng the role of sun exposure in the development of naevi in the Netherl ands, we found that the total naevus count had a significant associati on with cumulative sun exposure before the age of 12 as well as with t wo or more painful sunburns before the age of 12. In Curacao these rel ationships were not observed. In contrast, however, on Curacao the pre sence of atypical naevi showed an association (odds ratio = 2.6, 95% c onfidence interval 1.1-6.0) with the highest level of cumulative sun e xposure and with painful sunburns before the age of 12 (odds ratio = 2 .6, 95% confidence interval 1.2-5.5). In the Dutch group these associa tions were not significant. We hypothesize that in the development of banal naevi there is an association between the total number of naevi and sun exposure only at low exposure levels; however, after overstepp ing a critical threshold a further association between melanocytic nae vi and sun exposure is lacking. Sunlight exposure before the age of 12 plays a complex role: only very high exposure levels seem to contribu te to the development of atypical naevi.