Metastatic extraosseous Ewing tumor: Association of the additional translocation der(16)t(1;16) with the variant EWS/ERG rearrangement in a case of cytogenetically inconspicuous chromosome 22

In Ewing sarcoma and related tumors, recently referred to as the Ewing tumors (ET), t(11:22)(q24q12) and its molecular genetic equivalent, the EWS/FLI-1 rearrangement, characterize approximately 85% of cases, while variant aberrations are rare. A second nonrandom aberration in ET is the unbalanced t(1;16) accompanying the t(11;22) in roughly 17% of cases. We present a 17-year-old man with estraosseous ET and multiple metastases, in whom the only cytogenetically detectable chromosomal aberration was der (16)t(1:16)(q12:q11.2). This finding was confirmed by fluorescence in situ hybridization (FISH). Using the RT-PCR technique, a variant EWS/ERG fusion transcript was noted, resulting from a t(21:22) chromosomal rearrangement which recently demonstrated in roughly 10% of ET. However, data on possible biologic differences in EWS/FLI-1 versus EWS/ERG expressing ET are as yet unavailable. This is the first reported combination of t(1;16) with the EWS/ERG rearrangement. A possible significance of this finding for Ewing tumor progression is discussed.