FISH analysis for EWSR1 gene rearrangement in Ewing sarcoma/PNET

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To investigate the usefulness of newly developed probes to detect EWS rearrangement results from chromosomal translocations by the FISH technique using formalin fixed, paraffin embedded tissue in the clinical diagnosis of Ewing sarcoma (ES)/PNET, desmoplastic small round cell tumor (DSRCT) and clear cell sarcoma (CCS). Sixteen ES/PNETs, 6 DSRCTs and 6 CCSs were studied in this study. Three poorly differentiated synovial sarcomas (SSs), 3 alveolar rhabdomyosarcomas (RMSs) and 3 neuroblastomas (NBs) served as negative controls. Interphase FISH analysis was performed on FFPE tissue sections with a commercially available EWSR1 (22q12) dual colour, break apart rearrangement probe. As a result, the presence of one fused signal and one split signal of orange and green, which demonstrated rearrangement of the EWS gene, was detected in 14 of 16 (87.5%) ES/PNETs, 6 of 6 (100%) DRSCTs and 5 of 6 (83%) CCSs, but was not detected in the poorly differentiated SSs, alveolar RMSs and NBs. Interphase F … More ISH using this newly developed probe is sensitive and specific for detecting the EWS gene on FFPE tissues and is of value in the routine clinical diagnosis of ES/PNET, DSRCT and CCS.Similarly, we studied 33 RMSs (19 embryonal RMSs including three of sclerosing type and 14 alveloar RMSs). The fluorescence signals were detected for 18 of 19 (94.7%) Embryonal RMSs and 13 of 14 (92. 8%) alveolar RMSs. A split signal pattern was detected in 12 of 13 (92.3%) alveolar RMSs, but in none of embryonal RMSs including three of sclerosing type. Amplification and polyploidy were found to be present in both of embryonal RMSs and alveolar RMSs. Our FISH study highlighted an excellent performance of the commercial break apart probe for detecting rearrangement of the FKHR gene on RMSs. Amplification and polyploidy were detected in both of ERMSs and ARMSs, so be careful when counting the signals of the nuclei. No rearrangement of the FKHR gene found in all three of sclerosing type by FISH assay supported sclerosing RMSs might include embryonal RMSs. Less