PIK3R1 and pilocytic astrocytoma: While pilocytic astrocytoma and DNT can also harbor identical hotspot missense mutations in FGFR1, the combination of co-occurring FGFR1 p.N546 or p.K656 mutation together with either PIK3CA or PIK3R1 mutation in LGNET appears to be specific for RGNT and was not found in any epigenetically confirmed cases of pilocytic astrocytoma, DNT, and EVN in this cohort or the published literature to date [38, 40].