IDH1 and central nervous system cancer: Due to the observation that ATRX loss was restricted to the astrocytic phenotype, although the loss of H3K27me3 along with the retained ATRX was more consistent with the oligodendroglial phenotype, these authors suggested that 1p/19q codeletion testing could be reserved mainly to those IDH-mutant gliomas with retained ATRX and H3K27me3 immunohistochemical expressions [80].