IDH2 and oligodendroglioma: This latter study therefore questioned the assumptions of Filipski et al. that H3K27me3 retention can be used as the sole evidence against 1p/19q codeletion, and that the co-occurrence of H3K27me3 loss and retained or non-conclusive ATRX in IDH-mutant gliomas is specific to oligodendrogliomas [15].