(A) IGV (integrated genomic viewer) tool using RNAseq data showing FGFR4 kinase domain mutation at V548 position (exon 13) with a 49% allelic frequency and read coverage of 717 in SRMS17, compared with other RMS cases; (B) Bar chart showing high FGFR4 mRNA expression in ScRMS17, compared to other tumor types and RMS cases (including SRMS6 and SRMS7 with VGLL2-CITED2 fusions; 2 ectomesenchymomas [ECTM], 1 infantile myofibroma [MYO1] and other subtypes of RMS). Of note, similarly high FGFR4 expression was seen in an adult SRMS, lacking MYOD1, PIK3CA and FGFR4 mutation (adSRMS1). (C) IGV showing MYOD1
L122R mutation with a 42% allele fraction and read coverage of 883 and further confirmed by Sanger sequencing as a heterozygous mutation. (D) Bar chart showing overall high expression of MYOD1 mRNA across different RMS and ectomesenchymomas compared to other tumor types, with highest levels in the 2 cases harboring MYOD1 mutations (adSRMS2, SRMS17).