Prevalence and anatomical distribution of naevi in young Queensland children.

Sunlight is the principal environmental cause of melanoma and has also been implicated in the pathogenesis of melanocytic naevi. Epidemiological evidence indicates that childhood is a period during which melanocytes are susceptible to the effects of sunlight, yet little is known about the development of naevi in infancy. We conducted a survey of child-care centres to document the prevalence and anatomical distribution of melanocytic naevi among 193 young children aged 1-3 years in Brisbane, Australia (latitude 27 degrees S). Naevi were counted on all skin surfaces except for the scalp, buttocks and genitalia. Overall, almost 90% of children in the study sample had at least 1 naevus of any size, and more than 30% of children had 10 or more naevi. Total naevus counts ranged from 0 to 45 and were strongly determined by age. When taken together, naevus densities were highest on exposed body sites such as the face and limbs; however the density of large naevi (> or = 5 mm) was significantly higher on the trunk than on the face, neck and ears. These data support the concept that melanocytic neoplasia commences early in life and that naevus evolution is influenced by the anatomical site of the target cell.