Abstract:  Pilomatricoma is a benign tumor that presents as a 3–30-mm, firm, solitary, deep, dermal or subcutaneous tumor on the head, neck, or upper extremities. The clinical diagnosis is often made by the firm, sometimes rock-hard texture of the skin. The diagnosis can be confirmed by a skin biopsy or excision of the lesion. We have recently noted that pilomatricomas appear as a black mass in the skin when the lesion is transilluminated by placing the light of a fiberoptic otoscope adjacent to the skin lesion. To our knowledge, this is the first report demonstrating preoperative diagnosis of pilomatricoma by transilluminating the lesion with an otoscope.