Summary of the WHO revised IVth edition for CNS tumours

Abstract

The WHO classification of Tumours of the Central Nervous System was updated as per the revised 4th edition in 2016. The main change was that molecular parameters in addition to histology are now used to define many tumor entities. Therefore, the 2016 edition presents a major restructuring of the diffuse gliomas, ependymomas, medulloblastomas and other embryonal tumours. The new entities defined by both histology and molecular features include diffuse astrocytoma, IDH mutant and diffuse astrocytoma IDH-wildtype;oligodendroglioma IDH mutant and 1p19q-codeleted;glioblastoma, IDH-wildtype and glioblastoma, IDH-mutant;diffuse midline glioma, H3 K27M-mutant;RELA fusion-positive ependymoma;medulloblastoma, WNT-activated and medulloblastoma, SHH-activated;and embryonal tumour with multilayered rosettes, C19MC-altered. However, most of these molecular markers adopted for diagnosis could be surrogated by immunohistochemical studies. As such, this update may present a big challenge and in the transition period.