Practical implications of integrated glioma classification according to the World Health Organization classification of tumors of the central nervous system 2016

Abstract

Purpose of review: Morphological features identifiable by light microscopy have been the basis of brain tumor diagnostics for many decades. The revised WHO classification of tumors of the central nervous system 2016 combines histological and molecular features for an integrated classification. This new approach builds upon advances in brain tumor molecular genetics and has important practical implications.

Recent findings: Molecular genetic studies revealed distinct glioma entities with specific genetic and epigenetic profiles. Evidence has been accumulated that molecular classification more reliably discriminates glioma entities and better predicts patient outcome than histological classification. Major glioma entities can be distinguished by four molecular biomarkers included in the new WHO classification, namely isocitrate dehydrogenase mutation, codeletion of chromosome arms 1p and 19q, codon 27 lysine-to-methionine mutation in H3 histones, and C11orf95-RELA gene fusions. Each is detectable by common techniques in routinely processed tissue specimens. Their integration into glioma classification greatly improves diagnostic accuracy but also has practical implications concerning establishment and quality control of novel techniques, increased costs and prolonged time to diagnosis.

Summary: We summarize the relevant changes in the revised WHO classification of gliomas, outline the integrated approach, and discuss its practical implications and potential challenges.