Primary Orbital Ewing Sarcoma

: The authors report the clinical manifestations, pathologic character, management, and prognosis of primary orbital Ewing sarcoma, and review pertinent literature. A 6-year-old boy presented with the complaint of abruptly decreasing visual acuity and right proptosis. Computed tomography scan revealed a mass in the region of the right infratemporal orbit with extension into the infratemporal fossa and masseteric space, and there was erosion of the right lateral orbital wall. An anterior orbitotomy eyelid crease was performed to remove the tumor. The tumor cells were positive in membranous pattern for CD99 immunostaining; all other reactions were negative. The EWS-FLI-1 fusion gene was not detected by reverse-transcription polymerase chain reaction. Combined radiotherapy was applied. Primary orbital Ewing sarcoma is an extremely rare malignant tumor that shows a predilection for males (ratio: 1.4 to 1). Appropriate treatment consists of local resection, radiotherapy, and adjunctive chemotherapy.