EWSR1 and Ewing sarcoma: In contrast, the reciprocal fusion gene, FLI-1-EWS, has not been studied because the attempts to detect FLI-1-EWS mRNA expression in Ewing sarcoma mainly by Northern blotting were not successful [6, 13, 14] and the translocated chromosome encoding FLI-1- EWS can be lost secondarily in a small subset of Ewing sarcoma cells [15].