Pigmented Onychomatricoma: Clinical and Dermoscopic Findings in a Series of 29 Cases.

INTRODUCTION: Pigmented onychomatricoma is a rare benign fibroepithelial tumor of the nail matrix that may clinically simulate subungual melanoma and other pigmented nail disorders. Because of its rarity and overlapping presentation with malignant nail unit tumors, recognition of its characteristic clinicodermoscopic findings is essential to avoid misdiagnosis and unnecessary aggressive surgical procedures. METHODS: We retrospectively reviewed 29 patients with histopathologically confirmed pigmented onychomatricoma treated between 2015 and 2024. Demographic, clinical, and dermoscopic data were analyzed descriptively. RESULTS: Seventeen patients were men (58.6%) and twelve were women (41.4%), with a mean age of 54 years (range 31-71 years). Fitzpatrick phototype IV predominated (58.6%). Longitudinal melanonychia was present in all patients (100%). The most frequent clinical findings were increased nail thickness (96.6%), increased transverse curvature (72.4%), and xanthonychia (51.7%). The most frequent dermoscopic findings were distal free-edge cavities (89.7%), splinter hemorrhages (62.1%), and parallel nail ridges (58.6%). Toenails were more frequently affected than fingernails (58.6% versus 41.4%), and the hallux was the most commonly involved digit (31%). The coexistence of longitudinal melanonychia, nail thickening, and characteristic distal cavities represented the most distinctive clinicodermoscopic pattern. CONCLUSIONS: Pigmented onychomatricoma demonstrates a consistent clinical and dermoscopic profile characterized by longitudinal melanonychia associated with nail thickening, characteristic distal cavities, and increased transverse curvature. Recognition of this constellation of findings is essential for differentiation from subungual melanoma and other pigmented nail tumors.