EWSR1 and Ewing sarcoma: Although this strategy could be useful to target the 85% of Ewing sarcomas harboring the EWSR1–FLI1 fusion gene, a different approach should be developed to target Ewing sarcomas with other gene fusions involving other ETS genes, such as EWSR1-ERG (10% of cases), and even other rarer gene fusions such as EWSR1-ETV1, EWSR1-ETV4, or EWSR1-FEV (5% of cases).