Loss of 1 of the 2 alleles at 11p15.5, a region that includes multiple imprinted genes encoding growth factors (e.g., IGF2) or growth suppressors (e.g., H19 and CDKN1C), occurs as a result of whole chromosome loss, deletion, or uniparental disomy.7,8 Somatic driver mutations involving the RAS pathway (NRAS, KRAS, HRAS, NF1, FGFR4) have been identified in ~50% of ERMS, and mutations in TP53 occur in 10% of ERMS and may be associated with histologic anaplasia.9,10. This evidence concerns the gene FGFR4 and embryonal rhabdomyosarcoma.