PAX--FKHR fusion genes and AChR-gamma in Chinese patients with rhabdomyosarcoma: diagnosis using formalin-fixed archival tissues.

The majority of alveolar RMSs have t(2;13)(q35;q14) or (1:13)(p36;q14),which generate PAX3/7 -FKHR fusion genes. Here, the authors detected the PAX3/7-FKHR fusion transcripts in 17 formalin-fixed, paraffin-embedded RMSs and 26 other SRCTs using one-step RT-PCR. PAX3 -FKHR and PAX7-FKHR transcripts were positive in 4/8 and 2/8 cases of ARMS, respectively. 9 ERMSs and 26 other SRCTs were negative for PAX3/7-FKHR. In addition, AChR-gamma and AChR-alpha mRNA were detected by semiquantitative duplex PCR in above cases and 3 normal muscles. 17 RMSs were found to have overexpression of AChR-gamma, with an AChR-gamma/-alpha ratio of > or =1; 3 cases of normal muscle had very weak AChR-gamma expression, with an AChR- gamma/-alpha ratio of <1. AChR-gamma transcripts were not detectable in all 26 other SCRTs. The results demonstrated that detection of PAX3/7-FKHR fusion gene by one-step RT-PCR is useful in the diagnosis of RMS and that AChR-gamma is overexpressed in Chinese RMS patients.