Whereas some tumor types have been incorporated in the 2021 WHO classification, other methylation classes are provisional (such as high-grade diffuse glioma of the midline/posterior fossa: H3/IDH-wildtype; adult-type diffuse high grade neuroepithelial tumor, IDH-wildtype, subtypes B/D) [2]. Here, IDH1 is linked to neuroepithelial neoplasm.