Ganglioneuroblastic differentiation in a primary cutaneous malignant melanoma.

Ganglioneuroblastic differentiation in malignant melanomas is an exceedingly rare event. Although there has been a single report of this occurrence in a metastatic melanoma, divergent ganglioneuroblastic differentiation has not been documented previously in a primary cutaneous lesion of melanoma. The present report describes an unusual case of invasive melanoma arising on the lower leg of a 61-year-old woman. The 16.9-mm thick tumor showed extensive ganglioneuroblastic differentiation, which was confirmed both immunohistochemically and ultrastructurally. Although the prognostic significance of this observation remains uncertain, the unique case reaffirms the potential morphologic diversity of melanomas and suggests a shared histogenetic origin from a common neural crest derivative.