Histologic features of congenital melanocytic nevi in infants 1 year of age or younger.

Abstract

Congenital melanocytic nevi (CMN) occur in approximately 1% of the white population. These lesions are often surgically excised prophylactically because of increased melanoma risk. In this study 87 CMN of all sizes from infants 12 months of age or younger (mean age, 6.6 months) were examined histologically. Each lesion was evaluated for depth of nevus cell involvement, overall epidermal and dermal pattern, and cytologic atypia. Most CMN involved the lower half of the reticular dermis (89%), and 51% infiltrated the subcutaneous tissue. Depth of nevus cell infiltration was positively correlated with size of the lesion. The predominant dermal pattern was diffuse interstitial infiltration (63%). Patchy nevus cell patterns were observed in 37% of the CMN and were associated with smaller lesions (p < 0.001). Most of the CMN displayed no cytologic atypia (70%), and we found no cases of melanoma. Atypia was not significantly associated with either size or location of the nevus. These results indicate that depth and pattern of nevus cells are directly related to size of CMN in infants.