The many faces of Ewing sarcoma: difficult to diagnose pediatric cases.

Ewing sarcoma (ES) is the second most frequent primary malignant bone cancer, following osteosarcoma. ES is a small round-cell tumor typically arising in the bones, rarely in soft tissues, of children and adolescents. We describe four children aged 3, 3.5, 9, and 9.5 years, who presented with two femur masses simultaneously (patient 1), a huge mediastinal mass (patient 2), an abdomino-mediastinal mass with dysphagia (patient 3), and a huge abdomino-pelvic mass (patient 4). Our patients were of younger age and had abnormal presentations that made initial diagnosis difficult, but also are representative of the different problems encountered in pediatric practice. Biopsy initially revealed round cell tumor and by immunohistochemistry, CD99 was positive, which confirmed the diagnosis of ES. Our patients were difficult to diagnosis.The patients were misdiagnosed initially, so there was a delay in diagnosis. Definitive diagnosis required use of various radiological imaging methods and immunohistochemistry.