PIK3CA and alveolar rhabdomyosarcoma: The two main subtypes are alveolar rhabdomyosarcoma (ARMS), which is associated with PAX3/7-FOXO1 fusion genes, and embryonal rhabdomyosarcoma (ERMS), which is associated with mutations in common cancer genes such as HRAS, KRAS, NRAS, CTNNB1, PIK3CA and TP531.