BCOR and Ewing sarcoma: Nevertheless, Ewing sarcomas, sarcomas with BCOR alteration, and mesenchymal chondrosarcomas frequently originate in bone with a broad site distribution but a preference for the long bones in Ewing sarcomas and sarcomas with BCOR alteration, as is also seen in (S)COS [2, 6, 7, 21–23].