A bullet-sired bone cyst.

Random gunfire deposited a bullet in the proximal tibial metaphysis of a 9-year-old girl. The wound was not incapacitating and was treated conservatively. Within 17 months, soreness developed in the proximal leg, and radiography revealed a large unicameral cyst within which the bullet freely tumbled. Eventually, fear of impending fracture prompted further radiography, computed tomography, surgical intervention and pathological examination of the cyst wall. We believe this is only the second description in the English-language literature of this rare sequence of events.