The naevus count on the arms as a predictor of the number of melanocytic naevi on the whole body.

A study of melanocytic naevi was carried out in southern Spain to examine the relationship between numbers of naevi at different body sites as predictors of whole-body naevus count and to determine whether the naevus count on the arms is valid for identifying the risk factors for total naevi. Subjects were the control group from a case-control study on risk factors for cutaneous melanoma. They were selected from visitors to the University of Granada Hospital (southern Spain) between 1989 and 1993. Of 200 people invited to participate, 146 accepted (73%). Data were collected by personal interview, and melanocytic naevi were counted over the entire body surface by clinical skin examination performed by one dermatologist. Partial correlation coefficients (R) estimated by multiple linear regression were calculated. Comparisons between whole-body naevi and naevi on the arms, and their relationship with risk factors, were assessed by analysis of variance and covariance. Arms in men (adjusted R = 0.88) and thighs in women (adjusted R = 0.82) were the best predictors of total naevi after adjusting for age and sun exposure. Age, occupational and leisure sun exposure, and sunburns showed significant correlations with the total number of naevi. Similar results were found for the naevus count on the arms. In conclusion, the prediction of whole-body numbers of naevi by a naevus count on specific sites differs between men and women: arms in men and thighs in women are the best predictors. Nevertheless, naevus counts on the arms allowed us to study the risk factors for total naevi as well as whole-body naevus count: age and occupational sun exposure were the strongest determinants.