Although the clustering analysis using only IDH-mutant samples (C.1–C.4) still could not clearly distinguish codel from non-codel tumors (Supplementary Fig. S1a), the futher analysis, using only C.1 and C.2 samples, did so, indicating that astrocytomas and oligodendrogliomas have their own characteristic methylation profile (Supplementary Fig. S1b). Here, IDH1 is linked to oligodendroglioma.