The Evolving Classification of Diffuse Gliomas: World Health Organization Updates for 2021

The upcoming 2021 World Health Organization (WHO) Classification of Tumours of the Central Nervous System will feature numerous changes in classification, diagnostic criteria, nomenclature, and grading of diffuse gliomas. This article reviews these changes and the clinical and molecular findings underlying them.

Since the publication of the 2016 World Health Organization (WHO) Classification of Tumours of the Central Nervous System, research has led to new insights into how molecular changes impact both the classification and grading of CNS tumors. The continued integration of molecular and histopathological features has led to changes in diagnostic criteria and grading for various tumors. In the new 2021 WHO CNS tumor classification scheme, diffuse gliomas will be classified as either adult-type diffuse gliomas, pediatric-type diffuse high-grade gliomas, or pediatric-type diffuse low-grade gliomas. The upcoming changes in the classification of adult-type and pediatric-type diffuse gliomas allow for more effective communication of both diagnostic and prognostic information, and-particularly in the case of pediatric-type diffuse gliomas-may suggest possible targeted strategies for therapeutic intervention.