EWSR1 and Ewing sarcoma: The role of insulin like growth factor-1 (IGF-1) and its receptor IGF-1R in the pathogenesis of Ewing’s sarcoma is well established.57 IGF-1R is found on the surface of most Ewing’s sarcoma cells and is necessary for the transforming ability of EWS-FLI fusion proteins.57 Thus, targeted therapy against IGF-1/ IGF-1R may be a very effective strategy in future.