Onychomatricoma

Onychomatricoma is a rare benign tumor originating from the nail matrix, the area where the nail plate grows. It is considered a subtype of a trichoepithelioma, a type of skin appendage tumor. These tumors are typically found in the nail matrix of fingernails or toenails and can present as a smooth, dome-shaped papule or nodule. The surface may be flesh-colored, pink, or erythematous. Onychomatricomas can grow slowly and may cause nail dystrophy, such as thickening, ridging, or onycholysis (nail separation from the nail bed). In some cases, they can be asymptomatic and discovered incidentally. Microscopically, the tumor is characterized by nests and cords of basaloid cells with peripheral palisading, similar to other trichoepitheliomas. Differentiated structures resembling hair follicles or sebaceous glands may also be present. Diagnosis is usually confirmed by histopathological examination of a biopsy specimen. Treatment typically involves complete surgical excision to ensure complete removal and prevent recurrence. The prognosis for onychomatricoma is generally excellent following complete excision, with no known malignant transformation reported. It is important to distinguish onychomatricoma from other nail matrix tumors and inflammatory conditions.