Onycholemmal Horn: A Distinctive Subungual Tumor

Onycholemmal horn (OH) is a rare subungual tumor originating from the nail bed, characterized by trichilemmal keratinization similar to hair follicles. It presents as an asymptomatic, keratotic, exophytic growth, primarily affecting elderly females with no history of nail trauma. Histopathologically, OH shows a distinctive orthokeratotic mass with compact lamellar keratin. Only two cases have been documented, highlighting its rarity and the importance of excisional biopsy for diagnosis. Differential diagnoses include Bowen's disease and squamous cell carcinoma. Surgical excision is the primary treatment, with no recurrences reported in the known cases. Further research is needed to better understand OH.