In addition, the presence of TERT promoter mutation in 2 of 3 RMS and lack of FOXO1 and other gene fusions in all 4 RMSs suggest a mucosal (urothelial) origin, probably representing extensive monomorphic rhabdomyoblastic transdifferentiation in SCNEC. Here, FOXO1 is linked to Bannayan-Riley-Ruvalcaba syndrome.