In situ reverse-transcriptase polymerase chain reaction demonstration of the EWS/FLI-1 fusion transcript in Ewing's sarcomas and peripheral primitiveneuroectodermal tumors

It is now widely accepted that the EWS/FLI-1 fusion transcript is associate d with tumors of the Ewing family. To test whether it is possible to detect the fusion transcript by means of combining polymerase chain reaction (PCR ) methodology and immunohistochemistry, we investigated tumors of the Ewing family using in situ reverse transcriptase (RT)-PCR. We were able to demon strate the t(11;22) fusion transcript in five of six cases of Ewing's sarco ma and four of four peripheral primitive neuroectodermal tumors. These resu lts were confirmed using fluorescence in situ hybridization in seven tumor samples. In situ RT-PCR-labeled fusion transcripts were found in virtually all tumor cells within a given sample, indicating that each cell possessed the t(11;22) transcript. We conclude from these results that in situ RT-PCR can be used for the rapid detection of EWS/FLI-1 fusion transcripts in bio psy material. The findings also suggest that all cells of the tumors of the Ewing family carry the EWS/FLI-1 fusion transcript.