Sankey plot displaying an overview of how the taxonomy of diffuse gliomas has changed over time; the size of the strips provides an indication of the relative frequency of the different tumour types. Since 2016 molecular characteristics are part of the definition of multiple gliomas. As a result, (anaplastic) oligoastrocytoma and gliomatosis cerebri are now generally recognized as another diffuse glioma type and their diagnosis has almost disappeared. Of note, different grades of glioma still had their own entry in the 2007 and 2016 classification (e.g., anaplastic astrocytoma = WHO grade III), but in the 2021 classification grades are assigned within types. Last but not least, after the introduction of diffuse midline glioma, H3K27-mutant in 2016, since 2021 more paediatric-type diffuse gliomas are included as separate tumour types in the classification. For the sake of clarity only diffuse midline glioma, H3K27-altered and diffuse hemispheric glioma, H3G34-mutant (both CNS WHO grade 4) are included in this diagram. The reader is referred to Supplementary Table 1 for all gliomas as listed in the WHO 2007, 2016 and 2021 classification of CNS tumours, respectively.