Further immunohistochemical staining was applied to rule out differential diagnoses of osteosarcoma, Ewing sarcoma, Ewing-like sarcoma (novel entities like CIC-DUX4 and BCOR-CCNB3 sarcomas), clear cell sarcoma of soft tissue, and other soft tissue tumors, e.g., rhabdomyosarcoma and synovial sarcoma. The gene discussed is DUX4; the disease is Ewing sarcoma.