[Revised WHO classification of brain tumours]

Abstract

The WHO classification of brain tumours has been widely accepted and used in daily medical practice for more than 25 years since the first edition was published in 1979. In 2007, WHO revised the former classification, and published the newest one, the 4th edition of WHO classification. This revision updated the concept of grading, added several new entities and variants, modified and reclassified tumours, and changed the terminology. Newly codified entities include atypical choroid plexus papilloma, angiocentric glioma, extraventricular neurocytoma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, anaplastic hemangiopericytoma, Ewing sarcoma - PNET, pituicytoma, and spindle cell oncocytoma of the adenohypophysis. If a given tumour has an evidence of a different clinical features, genetic profile or prognostic behavior, it was considered to be histological variants; these included pilomyxoid astrocytoma, medulloblastoma with extensive nodularity, and anaplastic medulloblastoma. An overview of the 4th edition of WHO classification and short comments for each major point of alterations will be provided in this review.