Furthermore, the cooccurrence of FGFR1 and PIK3CA hotspot mutations was observed in two tumors pathologically diagnosed as oligodendroglioma and ependymoma (P2233_109T, P7708_112T), and both were assigned to the methylation class low-grade glioma, rosette-forming glioneuronal tumors. Here, PIK3CA is linked to oligodendroglioma.