Relationship of lumbosacral nevocytic nevi to sun exposure in dysplastic nevus syndrome.

In 104 consecutive Caucasian patients who had histologically proved dysplastic nevi, the number and diameter of nevocytic nevi were determined in two equally sized contiguous rectangles in the lumbosacral region. The cephalad (superior) rectangle was in a relatively sun-exposed site, whereas the caudad (inferior) rectangle was in a relatively sun-protected site. Many of the nevocytic nevi identified in these rectangles had the clinical features of dysplastic nevi. Significantly, more nevi were found in the cephalad rectangle compared with the caudad rectangle. Men greater than or equal to 40 years of age had significantly larger nevi in the cephalad rectangle compared with the caudad rectangle. These data are consistent with the hypothesis that sunlight promotes development of more and larger nevocytic nevi in individuals afflicted with dysplastic nevus syndrome.