The largest published study examined EWSR1-FLI1 and EWSR1-ERG transcript levels in the bone marrow and peripheral blood taken at the time of diagnosis of ES in 172 patients, 140 of whom were enrolled on French Society of Pediatric Oncology (SFOP) protocols and therefore received similar therapy (Schleiermacher et al., 2003). Here, EWSR1 is linked to Ewing sarcoma.