Spindle Cell/Sclerosing Rhabdomyosarcoma : Molecular Genetics
Molecular Genetics of Spindle Cell/Sclerosing Rhabdomyosarcoma (RMS): MYOD1 mutations are found in between 40% to 50% of spindle cell/sclerosing RMS in both pediatric and adult groups. These cases are characterized by aggressive behavior and poor outcome. A subset of MYOD1 mutant cases have coexisting PIK3CA mutations. Rare cases have mutations in FGFR4. The congenital/infantile form of sclerosing/spindle cell RMS is characterized by gene fusions involving VGLL2 and NCOA2 or CITED2 genes. Less common are TEAD1-NCOA2 and SRF-NCOA2 fusions. Another group of spindle cell/sclerosing RMS is fusion-negative and mutation-negative. It tends to involve paratesticular or intraabdominal locations and has good prognosis.