MYOD1 and rhabdomyosarcoma: They harbor recurrent gene fusions involving critical transcriptional activators of muscle-specific genes, such as VGLL2, NCOA2, and SRF, and have very good prognosis.13 (2) MYOD1-mutant spindle cell/sclerosing rhabdomyosarcoma (L122R in MYOD1), with or without accompanying PIK3CAmutations, occurring in older children in the head and neck and following a highly aggressive course.