KMT2D and rhabdomyosarcoma: Consistent with previous results,[1] we observed a mutation in NF1, a master regulator of the Ras signaling pathway,[7]NF1 mutations have also been observed in rhabdomyosarcoma.[8,9] Both rhabdomyosarcoma and histiocyte-rich rhabdomyoblastic tumors differentiate from skeletal muscle cells, and NF1 regulates the growth and metabolism of muscle tissues.[10] In addition, we observed mutations in DNMT3A and KMT2D, which encode methyltransferases,[11] suggesting that methylation is involved in the development of histiocyte-rich rhabdomyoblastic tumors.