FLI1 and Ewing sarcoma: Recent focus on fusion proteins has opened avenues for identifying novel therapeutic targets, exemplified by FUS-C/EBP HOmologous protein (FUS-CHOP) in myxoid liposarcoma and EWS RNA-binding protein 1/friend leukemia virus integration 1 (EWSR1/FLI1) in Ewing's sarcoma 139, 140.