“…Notably, FGFR1 alterations are not commonly found in IDH-wildtype glioblastoma in adults, IDH-mutant astrocytoma, IDHmutant and 1p/19q-codeleted oligodendroglioma, H3.3 G34-mutant diffuse hemispheric glioma, ganglioglioma, polymorphous low-grade neuroepithelial tumor of the young (PLNTY), papillary glioneuronal tumor, myxoid glioneuronal tumor, multinodular and vacuolating neuronal tumor, diffuse leptomeningeal glioneuronal tumor (DLGNT), central neurocytoma, and ependymomas of any location or subtype [5,6,8,9,16,17,23,24,26,28,29]. However, fusions involving other FGFR genes are recurrently found in PLNTY (mostly involving FGFR2) and IDH-wildtype glioblastoma in adults (mostly involving FGFR3, typically with TACC3 as the fusion partner) [4,10,17,39]. Therefore, while the identification of an FGFR1 alteration in a CNS tumor of uncertain subtype may help to narrow the differential diagnosis and exclude certain tumor entities, this single genetic finding in and of itself does not enable precise classification.…”