Adam I. Rubin

This report describes the clinical, onychoscopic, nail clipping, and histopathologic features of a malignant onychopapilloma. A 71‐year‐old male presented to our outpatient clinic for a stable, asymptomatic lesion on his left middle finger that had been present for 2 years. Prior nail clipping histopathology showed nail plate thinning with subungual abnormal onychocytes. Clinical examination revealed a 2‐mm‐wide streak of longitudinal xanthonychia extending to the proximal nail fold, with distal hyperkeratosis and onycholysis. Onychoscopy showed irregular longitudinal nail plate ridging with scattered punctate hemorrhagic foci. An excisional nail unit biopsy demonstrated cellular atypia of the nail bed epithelium, matrix metaplasia, longitudinal abnormal onychocytes, increased Ki‐67 staining, and negative HPV immunoperoxidase staining, confirming the diagnosis of malignant onychopapilloma.