Regression of Congenital Melanocytic Nevus with Halo Phenomenon Induced by Serial Excision

Abstract

Congenital melanocytic nevus is a hamartoma derived from the neural crest that is present at birth. Regression following surgical excision with an apparent halo phenomenon through suture lines has never been reported. A nine-year-old boy presented with a solitary symmetric, oval-shaped, blackish pigmented patch on his right forearm. He reported increasing size of the lesion with no other subjective symptoms. Histological examination of the first excisional biopsy revealed congenital melanocytic nevus, and serial excisions were planned. Interestingly, at the second visit at 18 months after the first biopsy, the size of the congenital melanocytic nevus was reduced with a peripheral whitish halo. Linear regression through suture lines and a peripheral halo was observed after the second and third serial excisions. The mechanism of the halo phenomenon remains elusive but is suggested theorized to be caused by destruction of melanocytes by immune responses of autoantibodies or cytotoxic T cells.