PIK3R1 and neoplasm: Together with the prior study by Sievers et al. [36], our findings further confirm that RGNT is a unique glioneuronal tumor type with both a distinct epigenetic signature and distinct combination of FGFR1 hotspot missense mutation together with mutually exclusive mutation of either PIK3CA or PIK3R1, the latter of which is a novel finding of this study.