Melanocytic nevi in a Brazilian community of predominantly Dutch descent (1999-2007).

BACKGROUNDS Epidemiological studies have shown a significant relationship between melanocytic nevi and cutaneous melanoma. OBJECTIVE To evaluate the development of melanocytic nevi in the pupils of a school composed primarily of children of Dutch descent and to assess the effect of environmental factors on these individuals whose phenotypic characteristics were similar to those of their ancestors. METHODS In 1999 a cohort study was initiated to count the number of melanocytic nevi in 282 pupils of 3 to 17 years of age, 53.9% of whom were boys. Five years later a repeat exam was conducted in 148 students of 8 to 22 years of age, 49.3% of whom were males. The association between the age, skin phototype, eye color, hair color and ethnic group of the pupils and their parents and the presence of melanocytic nevi was analyzed at the beginning and at the end of the study. RESULTS There was a significant increase in cases of melanocytic nevi and dysplastic nevi at the follow-up examination. The number of melanocytic nevi was greater in boys than in girls in both covered and exposed areas of skin. Likelihood analysis calculated using the odds ratio showed that boys were more likely to develop melanocytic nevi than girls and that the children of non-mixed and mixed race with lighter hair were more likely to develop melanocytic nevi than those of other ethnic groups and those with dark hair. Children with skin phototype I were more likely to develop melanocytic nevi in covered areas of skin compared to those with skin types II or III. CONCLUSIONS These data show that individuals of Dutch descent were more likely to develop melanocytic nevi than individuals of other ethnic origins.