A and B, Anteroposterior and lateral radiographs of left fibula of 7-year-old girl with Ewing sarcoma. Involvement of large portion of bone (or even entire bone) is typical of Ewing sarcoma. C, MR image shows a large soft-tissue mass. D, Typical microscopic appearance of Ewing sarcoma. E and F, Anteroposterior and lateral radiographs after completion of neoadjuvant chemotherapy. Note increased ossification of lesion. G, Repeat MR image after neoadjuvant chemotherapy shows marked reduction in size of soft-tissue mass. H and I, Anteroposterior and lateral radiographs of left tibia after wide resection of tumor. Distal fibular physis was preserved. Wide resection avoids complications associated with radiation therapy in growing child.