IDH1 and oligodendroglioma: Immunohistochemical analysis for H3K27me3, ATRX, and IDH1-R132H revealed that diffuse gliomas with a loss of nuclear H3K27me3 staining, retained ATRX staining, and IDH1-R132H positivity can be predicted as 1p/19q codeleted oligodendrogliomas with a probability score of 0.9835.