Sex differences in the anatomical distribution of melanocytic nevi in Canadian Hutterite children.
BACKGROUND: Studies of the distribution of melanocytic nevi (MN) and/or cutaneous malignant melanoma (CMM) in white populations have commonly observed greater numbers of MN and CMM on the torsos of males and on the limbs of females. The most commonly cited explanation for this sex difference is differential sunlight exposure of body subsites due to gender differences in clothing styles and recreational activities. Less common, but more speculative, explanations suggest hormonal differences or regional differences in melanocytes across body subsites. OBJECTIVE: The purpose of the present study was to evaluate these explanations in light of sex differences in the anatomical distribution of nevi in Canadian Hutterite children whose traditional religious costume protects them from sun exposure. METHODS: Nevi counts from 178 male and 154 female children, aged 5 to 15 years, from 23 Central Alberta Hutterite colonies were broken down by age and body subsite. RESULTS: At age levels from 6 to 15 years, males had greater nevus counts on the torso, whereas females had greater counts on the upper and lower limbs. CONCLUSION: The appearance of this distribution of nevi in sun-protected children as early as age 6 is problematic for explanations based on differential sunlight exposure and hormonal changes at puberty.