Classification of Tumours of the Central Nervous System

CNS tumours include both primary and secondary neoplasms. The classification of primary CNS tumours has been significantly updated by the latest WHO classification (4th Edition, Revised), published in 2016. Molecular parameters, which were previously considered supplementary information, are now used to define CNS tumours by employing an integrated histological-molecular classification. This novel approach allowed to define specific entities which are more consistent in terms of phenotypical, genotypical and clinical characteristics, compared to the previous criteria which were based on histopathological findings alone. Diffuse gliomas are a paradigmatic example of this novel approach: the newly introduced classification, which is mainly based on two molecular alterations (IDH1/IDH2 mutation and 1p/19q codeletion), allows to recognize specific prognostically relevant entities, despite possible morphological ambiguities. These changes will hopefully help provide the best possible care to patients.