ABSTRACT
BACKGROUND: since congenital nevi may not always be identified clirically, it remains a challange for histologists to separate an acquired from a congehital nevus. The camparative histologic feature of congenital and acquired lesions have been described by several authors. OBJECTIVE: In an attempt to establish reliable microscopic recognition of congenital nevi, the histologic features of 52 congenital melanocytic nevi were studied. MATERIAL AND METHODS: By reviewing HMB slides, histologic paterns were observed depending on the extent of nevus cell infiltration. An immunohistochemical study wi h anti S-100 protein and HMB-45 antibody was also performed. RESULTS: Diffuse infiltratien of upper and lower dermis with nevu. cells was observed in 21 cases (40.0%). Nevus cell infiltration of appendages and neurovascular structures was observed in 29 cases (55.8%). Indian filing of dermal nevus cells was observed in 33 casesl(64.7%). Epidermis showed elongation of rete ridges in 36 ca.es(69.2%). Immunohistochemical staining with HMB 45 showed a positive raction in 9 cases out of 51 having dermal nevus cells, and epidemal melanocytes showed positive reaction in 20 cases. CONCLUSION: Congenital melanocytie nevi can be classified by histolcgic appearance into several patterns. Nevus cells had a trend to infiltrate into the deeper dermis as the clinieal size increrased. Nevus cell infiltration of appendages and neurovascular structure was a common finding in congenital melanocytic nevi.