Rare Subungual Fibroepithelial Polyp With Keratosis: Differential Diagnosis.

Fibroepithelial polyps (FEPs), commonly known as acrochordons or skin tags, are benign cutaneous lesions typically found in intertriginous areas, such as the neck, axilla, and groin. Occurrence within the nail unit is exceptionally rare, presenting a diagnostic challenge as it mimics more common ungual tumors. We report a rare case of a 23-year-old woman who presented with a 4-year history of a painful, slow-growing lesion emerging from the proximal nail fold of the right fifth toe, causing nail plate deformity. Clinical differentials included acquired ungual fibrokeratoma and Koenen tumors. The lesion was completely excised, and the base was ablated. Histopathological examination revealed a FEP with keratosis, characterized by a loose collagenous core, distinguishing it from the dense vertical collagen typical of fibrokeratomas. Although FEPs are common skin lesions, their presentation in the nail unit is unusual. This case highlights the importance of considering FEP in the differential diagnosis of subungual and periungual tumors. Complete excision with ablation of the base was curative and prevented recurrence.