IDH1 and oligodendroglioma: Twelve patients with de novo or progressive HGG, including glioblastoma (IDH-wildtype) (n = 6) and oligodendroglioma (IDH-mutated, 1p/19q codeleted) (n = 1), or a secondary brain tumour from lung- (n = 4) or breast- (n = 1) carcinoma, were included.