KRAS and Ewing sarcoma: Our study shows that 21.4% of patients (6 of 28) with advanced, heavily pretreated Ewing's sarcoma family of tumors (ES, n = 18; DSRCT, n = 10) had secondary somatic molecular aberrations, including mutations in KRAS, PTPRD, GRB10, MET and PIK3CA. Interestingly, we recently reported germline PTPRD mutations in three out of eight (37.5%) patients with metastatic Ewing's sarcoma [21].