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 ifs molecular genetic equivalent, t he EWS/FLI-1 rearrangement, characterize approximately 85% of cases, w hile variant aberrations are rare. A second nonrandom aberration in ET is the unbalanced t(1;16) accompanying the tt(11;22) in roughly 17% o f cases. We present a 17-year-old man with estraosseous ET and multipl e 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 techniq ue, a variant EWS/ERG fusion transcript was noted resulting from a t(2 1;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 firs t reported combination of t(1;16) with the EWS/ERG rearrangement. A po ssible significance of this finding for Ewing tumor progression is dis cussed.