Unusual Clinical Presentation of Regression in a Congenital Melanocytic Nevus

Abstract

Regression of congenital melanocytic nevi is usually accompanied by the halo phenomenon and is considered a rare event. A 15-year-old woman presented for the evaluation of multiple halo nevi. She had on her trunk a figure-of-eight pigmentary lesion, which had been developed after the coalescence of two distinct congenital melanocytic nevi. Close to the indentation between the two portions of the lesion, there was an achromic rounded area, extending from the perinevic skin to the nevus, causing its partial regression. Dermoscopic examination disclosed a globular and homogeneous pattern, which was irregularly present at the edge of the achromic area. The histopathologic diagnosis was compound congenital melanocytic nevus with an eccentric area of regression. In our case, the presence of a regression area in the surrounding skin and the association with multiple halo nevi suggest a similarity with halo phenomenon, despite the atypical "halo," which was discontinuous and eccentric.