EWS/FLI-1 rearrangement in small round cell sarcomas of bone and soft tissue detected by reverse transcriptase polymerase chain reaction amplification.

Recent cloning of the t(11;22) region has led to the detection of a number of sequences involved in the breakpoints by substituting a sequence which encodes a putative RNA binding domain for that of the DNA binding domain of the human homologue of murine FLI-1. Several tumours display consistent translocation at t(11;22) (q24;q12), a finding that suggests these fusion transcripts could be expressed and detected by reverse transcriptase polymerase chain reaction amplification. To date, only a small number of Ewing's sarcomas (Es) and peripheral neuroectodermal tumours (pPNET) of bone have been tested with this novel molecular biology approach. In this study, we confirmed the presence of the three putative chimaeric transcripts on 7 cases of Es and pPNET sarcomas of bone and soft tissue, providing 100% positivity for the tested tumours. For comparative purposes, a number of other neuroectodermal tumours were analysed with negative results: esthesioneuroblastoma, retinoblastoma, Schwannoma. A primitive soft tissue sarcoma (ectomesenchymoma) with a 22 chromosome rearrangement did not express any transcript, nor did a number of non-neuroectodermal small round cell sarcomas of soft tissue (rhabdomyosarcomas) and bone (microcellular osteosarcoma), conventional bone sarcomas, leiomyosarcomas, malignant fibrous histiocytomas and synovial sarcomas. These results reinforce the value of molecular biology techniques for the correct assessment of histology difficult evaluable neoplasms, such as the group of small round cell tumours within the Es family.