Diagnostic Studies. Radiographs show a permeative usually diaphyseal tumor with a mottled, or patchy, density that indicates the tumor’s destructive nature. Cortical involvement frequently produces a reactive, “onionskin” appearance of the periosteum, a pattern of layered ossification, or Codman’s triangle suggestive of an aggressive lesion. The differential diagnosis includes osteomyelitis, osteolytic osteosarcoma (see Plate 6-14), and eosinophilic granuloma (see Plate 6-10).

Bone scans demonstrate intense radioisotope uptake well beyond the limits seen on radiographs and can reveal multiple skeletal lesions. MRI is used to determine local extent and soft tissue involvement and may reveal extensive areas of bony involvement.

Histologic features are small, round, neoplastic “blue” cells with large, hyperchromatic nuclei that do not make a calcified matrix. These small cells are usually spread out in thick sheets. The diagnosis is supported by the presence of EWSR1 fusion transcripts from translocation involving chromosome 22.

Treatment/Prognosis. Management of Ewing sarcoma has changed significantly since the effectiveness of various combinations of chemotherapy, radiation therapy, and resection has been demonstrated. Pulmonary metastases have been reduced, and patient survival has improved so that nearly 70% of patients who present without metastatic or multifocal disease survive.

Wide surgical resection is preferred over radiation therapy for local control if (1) the involved bone is reliably reconstructable, (2) the involved bone is expendable (e.g., fibula, rib, clavicle), (3) radiation treatment would cause significant growth deformity (e.g., in young children with growth plate involvement), (4) radiation treatment would cause significant risk of secondary postirradiation sarcoma such as in patients younger than 15 years old, or (5) previous local irradiation was unsuccessful.