 Previous studies of the PAX3-FKHR and PAX7-FKHR gene fusions in alveolar rhabdomyosarcoma (ARMS) indicated that the corresponding fusiontranscripts are not detectable in 20% of ARMS cases.     ///    Additional fluorescence in situ hybridization analysis identified two cases in which a PAX3-FKHR or PAX7-FKHR genomic fusion is present but is not associated with a fusion transcript detectable by RT-PCR.     ///    "In summary, our analysis of ARMS cases without characteristic PAX3-FKHR or PAX7-FKHR transcripts identified several genetically distinct subsets including low expression or atypical presentation of standard fusions, variant fusions with other genes, and possibly true fusion-negative cases.. "    ///    "To investigate the genetic features of this ARMS subset, we identified 23 ARMS cases in which PAX3-FKHR and PAX7-FKHR transcripts were not detected by a standard sensitivity reverse transcription-PCR (RT-PCR) assay. "    ///    Subsequent analysis with a high sensitivity RT-PCR assay identified low-level expression of PAX3-FKHR or PAX7-FKHR in three cases. 