Ewing's sarcoma of the humerus mimicking fibrous dysplasia on imaging and biological behavior.

We present the case of a 12-year-old girl who presented with a pathological fracture through a benign-appearing osteolytic lesion that was presumed to represent fibrous dysplasia. The fracture healed, and over the next 2.5 years there was further refracturing and healing with progressive osteolysis. A biopsy was performed and revealed Ewing's sarcoma. The disease was locally controlled by neoadjuvant chemotherapy and radiation therapy. The patient is disease free with excellent function 6 years following the discovery of the lesion. We illustrate and discuss the sequence of events.