Onychopapilloma: its clinical, dermoscopic and pathologic features

Onychopapilloma is a benign tumour of the nail bed and distal matrix and commonly presents as longitudinal erythronychia, longitudinal leukonychia or longitudinal melanonychia. Because onychopapilloma is rare, its clinical characteristics and dermoscopic findings have not been well investigated in Asia.This study aimed to investigate the clinical characteristics and dermoscopic and pathologic findings of onychopapilloma in Korea.We retrospectively reviewed the medical records and clinical/dermoscopic photographs of 39 patients diagnosed with onychopapilloma in the Pusan National University Hospitals (Busan and Yangsan) for 11 years (2010-2021).Among 39 patients, 23 (59.0%) were men, and 16 (41.0%) were women. The mean age was 46.1 (16-77) years. All lesions were single, and most of them were located on the fingers (92.3%), especially the thumb (66.7%). The most common clinical feature was longitudinal erythronychia (56.4%), and the most common dermoscopic finding was distal subungual hyperkeratosis (100%). We found two new dermoscopic features: macrolunula and trailing lunula along the longitudinal band. Among 18 patients who underwent surgical excision, only 6 (33.3%) showed typical acanthosis and papillomatosis on the nail bed.We found that Asian onychopapilloma has similar clinicodermoscopic findings to the Caucasian one, that is to say, longitudinal erythronychia and distal subungual hyperkeratosis were the most common nail change and dermoscopic finding, respectively. We propose two new dermoscopic features of onychopapilloma: macrolunula and trailing lunula along the longitudinal band.