About 60% of RMS initially diagnosed as ARMS and reclassified as other subtypes of RMS, except ERMS, showed a diffuse positivity, although only rarely comparable to that of t+ ARMS; while, in control ERMS and in ERMS formerly diagnosed as ARMS, DAX-1 was present in 17% and 0% respectively. This evidence concerns the gene KIDINS220 and alveolar rhabdomyosarcoma.