IMMUNOSTAINING OF THE P30 32(MIC2) ANTIGEN AND MOLECULAR-DETECTION OFEWS REARRANGEMENTS FOR THE DIAGNOSIS OF EWINGS-SARCOMA AND PERIPHERALNEUROECTODERMAL TUMOR/

The identification of Ewing's sarcoma (ES) and peripheral neuroectoder mal tumor (PNET) among other small round cell tumors (SRCTs) is a crit ical issue in musculoskeletal pathology because of the lack of clearly distinctive morphological features. In this study, the authors have c ompared advantages and limits of two procedures that were recently sug gested as additional tools for the identification of ES/PNET, the anal ysis of p30/32(MIC2) antigen by immunohistochemistry, and the evaluati on of the fusion products of two specific chromosomal aberrations, the t(11;22)(q24;q12) and the t(21;22)(q22;q12), by reverse transcriptase -polymerase chain reaction (RT-PCR). The authors have analyzed the exp ression of p30/32(MIC2) in 28 cell lines and in 90 tumor samples. p30/ 32(MIC2) was highly expressed in ES/PNET but was also present in all t he other cell types. The broad spectrum of positivity for p30/32(MIC2) in SRCTs of bone was substantially confirmed by the analysis of tissu e samples. In the same material, the authors have evaluated the presen ce of t(11;22) or t(21;22) transcripts (EWS/FLI-1 and EWS/ERG, respect ively) by RT-PCR. These transcripts were found in all the cell lines a nd tissue samples of ES/PNET, but not in other tumors. The authors' re sults question the use of p30/32(MIC2) immunostaining alone for the id entification of ES/PNET and suggest the adoption of RT-PCR as an advan tageous alternative. Molecular diagnosis of ES/PNET by RT-PCR is highl y specific and can be applied to small amounts of tissue. Moreover, RN A extracted from paraffin-embedded specimens was shown to be suitable for RT-PCR analysis, thus enabling analysis of archival material. (C) 1996 by W.B. Saunders Company