Clinicopathologic features of 28 cases of nail matrix nevi (NMNs) in Asians: Comparison between children and adults

Abstract

Clinical distinction between nail matrix nevus (NMN) and subungual melanoma (SUM) can be challenging. More precise delineation of the clinicodermoscopic characteristics specific for NMNs is needed. We sought to analyze the clinicopathologic features of childhood and adult NMNs and to propose clinicodermoscopic features that can aid in differentiating NMNs from SUM. We retrospectively reviewed clinical, dermoscopic, and histologic findings of patients (20children and 8 adults) in whom NMN was diagnosed between 2012 and 2015. Except for 2 cases of total melanonychia, the affected nails demonstrated longitudinal melanonychia sharply demarcated from the adjacent nail plate. Melanonychia was wider among children than among adults (P=.002). Nail dystrophy was more frequent in wider lesions (P=.028). Hutchinson's sign was observed in pediatric cases at the hyponychium and/or proximal nailfold cuticles. All hyponychial pigmentations demonstrated a longitudinal brush pigmentation pattern under dermoscopy. This was a retrospective study of Asians in a single center. Our study is the largest case series to date of biopsy-confirmed NMNs. It highlighted important clinicodermoscopic differences between pediatric and adult NMNs. We propose that in pediatric cases of longitudinalmelanonychia presenting as a sharply demarcated pigment band of even width, the presence of Hutchinson's sign with longitudinal brush pigmentation may favor a diagnosis of NMN over SUM.