HISTOLOGIC FEATURES OF CONGENITAL MELANOCYTIC NEVI IN INFANTS 1 YEAR OF AGE OR YOUNGER

Background: Congenital melanocytic nevi (CMN) occur in approximately 1% of the white population, These lesions are often surgically excised prophylactically because of increased melanoma risk. Objective: In this study 87 CMN of all sizes from infants 12 months of age or younger (mean age, 6.6 months) were examined histologically. Methods: Each lesion was evaluated for depth of nevus cell involvement, overall epidermal and dermal pattern, and cytologic atypia. Results: 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. Conclusion: These results indicate that depth and pattern of nevus cells are directly related to size of CMN in infants.