Recurrent halo nevus: Dermoscopy and confocal microscopy features

HN: halo nevi RN: recurrent nevi RCM: reflectance confocal microscopy INTRODUCTION Melanocytic nevi change throughout a person’s life. Most melanocytic nevi are acquired during childhood and early adulthood; in later life, the prevalence of melanocytic nevi falls. Nevi frequently form, but the exact mechanisms involved in their generation remain unknown. Nevi usually progressively fade or, less commonly, transition through targetoid presentations (halo, cockade, or Meyerson nevi). In halo nevi (HN), a symmetrical hypopigmented rim can be observed surrounding a central nevus. The progressive involution of the central part of this variety of nevus might be seen over the course of months to years, disappearing completely in 50% of cases. HN are more commonly associated with benign melanocytic nevi, but rarely occur in nevi with various degrees of atypia, in nonmelanocytic tumors, in inflammatory lesions, and in melanoma. The risk for malignancy often leads to the clinical investigation and follow-up of doubtful lesions. Dermoscopic examination of HN typically shows a globular or homogeneous pattern. Reflectance confocal microscopy (RCM) of HN has been previously described in 2 studies and some atypical features, also seen in atypical melanocytic lesions and malignant melanoma, were observed in most patients evaluated. These features included pagetoid cells, non-edged papilla, junctional thickening, nucleated cells in the dermal papillae, and plump bright cells. These atypical findings might be due to local inflammation.