EWS/FLI-1 fusion signal inserted into chromosome 11 in one patient with morphologic features of Ewing sarcoma, but lacking t(11;22)

A reciprocal t(11;22)(q24;q12) is found in 85% of Ewing sarcomas (ES) cases. We report a case of a child with ES, in whom trisomy 8 was observed as the sole chromosomal abnormality. Fluorescence in situ hybridization—using a set of probes that localize to 22q12 (EWS) and 11q24 (FLI-1) and usually show the translocation as fusion (red-green) signal on der(22)—showed a fusion signal on der(11) suggesting an insertion as the mechanism that led to the EWS-FLI-1 gene rearrangement. Reverse transcriptase-polymerase chain reaction studies revealed the presence of two EWS/FLI1 fusion gene products.