A 5-year-old girl with an enlarging mass at the elbow

Pilomatrixoma is a rare benign neoplasm that presents as a solitary, hard, mobile, subcutaneous mass. Pilomatrixomas can be found on any hair-bearing region of the body, with the upper extremity being the second most common location. Pilomatrixomas are common in children, and have a higher frequency in girls. We present a case of left-arm pilomatrixoma in a 5-year-old girl. Surgical excision was curative. Pediatric orthopedic surgeons should be familiar with this benign tumor when evaluating a calcified soft-tissue mass in the extremities of a child.