Giant Cell Tumor in an Immature Skeleton

We report a case of giant cell tumor occurring in a 12-year-old girl. Radiographs revealed a radiolucent lesion in the proximal epi-metaphysis of the right fibula, which was initially diagnosed as an aneurysmal bone cyst. Magnetic resonance imaging showed an expansile intramedullary lesion with focal multiloculated fluid-fluid levels and also solid mass in the proximal metaphysis. The latter solid component also extended into the proximal fibular epiphysis. Following the magnetic resonance imaging, the diagnosis was revised to giant cell tumor with focal aneurysmal bone cyst changes, which was subsequently confirmed histopathologically following surgery. The unusual occurrence, location, imaging features, and differential diagnosis of osseous giant cell tumor in the immature skeleton were discussed.