PAX3 and alveolar rhabdomyosarcoma: Given our findings, we believe that targeting FGFR4 will be most effective in ERMS with high expression (due to amplification) or mutation of FGFR4 or in alveolar rhabdomyosarcoma (ARMS) where the PAX3/7-FOXO1 fusion gene found in ARMS directly increases expression of FGFR4.