Application of fluorescence in-situ hybridization and reverse transcription-polymerase chain reaction in molecular diagnosis of Ewing's sarcoma and primitive neuroectodermal tumor

Objective: To detect tumor specific chromosome translocations and associated fusion transcripts in paraffin-embedded tissue by interphase fluorescence in-situ hybridization (FISH) and reverse transcription polymerase chain reaction (RT-PCR), respectively, and to evaluate their diagnostic values for Ewing's sarcoma/primitive neuroectodermal tumor (ES/PNET).

Methods: Nuclei of the tumor cells and total RNA were extracted from 10 cases of ES/PNET. Interphase FISH was utilized to analyze the EWS gene translocation with a dual color, break apart probe (Vysis company). RT-PCR was used to detect t (11; 22) (q24; q12) and t (21; 22) (q22; q12) fusion transcripts.

Results: Among 10 cases of ES/PNET, the EWS-FLI1 fusion transcript was detected in 8 by RT-PCR. EWS-ERG fusion transcript was not detected in any of the cases. EWS gene translocation was found in 9 of 10 cases by FISH.

Conclusions: Interphase FISH and RT-PCR can be reliably applied to paraffin-embedded tissues for molecular diagnosis of ES/PNET. Between the two approaches, interphase FISH provides a more sensitive and stable result.