Fusions of EWSR1 exon 7 to either FLI1 exon 6 (EWSR1-FLI1 type 1) or exon 5 (EWSR1-FLI1 type 2), account for 60% and 25% of Ewing sarcoma-Friend leukemia integration (EWS-FLI) fusions, respectively (2). Here, EWSR1 is linked to Ewing sarcoma.