Prevalence of acquired melanocytic naevi in Brazilian schoolchildren

The prevalence of acquired melanocytic naevi (AMN) is one of the most important known risk factors for malignant melanoma (MM) in homogeneous white populations. However, there are few studies on AMN in heterogeneous populations. Insight into the causes of AMN in heterogeneous populations in a country with intense ultraviolet radiation should lead to successful strategies in the prevention of MM.

To evaluate the frequency and anatomical distribution of AMN and to observe the influence of environmental and constitutional variables.

A cross-sectional study on the prevalence of AMN was performed on 1279 Brazilian schoolchildren, aged 2-8 years, according to an international protocol.

Both girls and boys had the same number of AMN. The number of AMN was higher on sun-exposed body sites, such as shoulders, thorax/upper abdomen, face/ears and back. A high number of AMN was associated with lighter skin type, greater sun exposure, age, number of sunburns and presence of freckles.

In genetically predisposed people, the body-site distribution of AMN in a heterogeneous population (mixed ethnic backgrounds) is similar to that in a homogeneous population and has the same tendency toward potential proliferation of melanocytes in the presence of ultraviolet radiation. Strategies to reduce the incidence of MM should start at an early age. We believe that these findings will have a direct effect on concepts for preventive strategies. Studies in different populations may serve as a starting point for research into the mechanism underlying increasing rates of AMN.