Introduction

Abstract

The 2021 WHO Classification of Central Nervous System tumors is a major advance in the field of neuro-oncology and neuropathology and represents a good example of translation of current molecular findings into a new classification system and more precise diagnostic criteria. Compared to the previous edition, in this fifth edition the integration of phenotypic and molecular genetic information in diagnostic categories has significatively increased. Moreover, the integration of epigenetic data through methylation profiling is the distinctive feature of this edition. In this issue of Pathologica, six review articles provide updates in the classification of major tumor categories relevant to diagnostic neuropathology according to the new WHO Classification. Antonelli and Poliani 1 discuss the current classification of diffuse gliomas in adults, including the role of ancillary molecular testing in identifying distinct tumor types (e.g., EGFR amplification, TERT promoter mutation, and +7/10 in glioblastoma, IDH wildtype) and grading (homozygous CDKN2A/B homozygous deletion in IDH mutant astrocytomas)