IDH1 and astrocytoma (excluding glioblastoma): In particular, mutations in the isocitrate dehydrogenase 1 (IDH1) encoding gene which are present in 70–80 % of LGGs confer a favorable outcome in astrocytomas [17] and discriminate lower-grade tumors with a rather benign clinical course from IDH1 wildtype (wt) tumors, that molecularly and clinically behave like glioblastoma [18].