The 2021 WHO classification of tumors, 5th edition, central nervous system tumors: the 10 basic principles

Excerpt

The 2021 WHO classification of tumors of the central nervous system (CNS), 5th edition (WHO CNS 5) [24] is built on the previous, revised 4th edition, published in 2016 (WHO2016CNS) [14], which incorporated molecular information into the diagnosis of brain tumors for the first time, breaking with the century-old histogenetic classification [1, 15]. The basic concept underlying WHO2016CNS was rooted in the Haarlem Consensus Guidelines [11] that aimed to establish instructions for incorporating molecular findings into the diagnosis of brain tumors and define diagnostic entities as narrowly as possible using molecular information. WHO CNS 5 also adopted a series of recommendations of “the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy (cIMPACT)” [2, 3, 5, 6, 16, 18‐20] that facilitates a consensus review of novel diagnostically relevant data and determines how such information can be fit into future CNS tumor classifications. Based on the above volumes and articles, the 5th edition moved molecular diagnosis forward [24]. However, the combination of histology and molecular information used to diagnose and grade CNS tumors remains at the center of tumor taxonomy [22]. …