Molecular diagnostic tools for the World Health Organization (WHO) 2021 classification of gliomas, glioneuronal and neuronal tumors; an EANO guideline

In the 5th edition of the WHO CNS tumor classification (CNS5, 2021), multiple molecular characteristics became essential diagnostic criteria for many additional CNS tumor types. For those tumors, an integrated, histomolecular diagnosis is required. A variety of approaches exists for determining the status of the underlying molecular markers. The present guideline focuses on the methods that can be used for assessment of the currently most informative diagnostic and prognostic molecular markers for the diagnosis of gliomas, glioneuronal and neuronal tumors. The main characteristics of the molecular methods are systematically discussed, followed by recommendations and information on available evidence levels for diagnostic measures. The recommendations cover DNA and RNA next-generation-sequencing, methylome profiling, and select assays for single/limited target analyses, including immunohistochemistry. Additionally, because of its importance as a predictive marker in IDH-wildtype glioblastomas, tools for the analysis of MGMT promoter methylation status are covered. A structured overview of the different assays with their characteristics, especially their advantages and limitations, is provided, and requirements for input material and reporting of results are clarified. General aspects of molecular diagnostic testing regarding clinical relevance, accessibility, cost, implementation, regulatory, and ethical aspects are discussed as well. Finally, we provide an outlook on new developments in the landscape of molecular testing technologies in neuro-oncology.

Automated summary

In the 5th edition of the WHO CNS tumor classification, molecular characteristics have become important diagnostic criteria for many CNS tumor types. This guideline focuses on the methods used for diagnosing gliomas, glioneuronal, and neuronal tumors using informative molecular markers. Various molecular methods are discussed, including next-generation sequencing, methylation profiling, and immunohistochemistry. The guideline also covers the analysis of MGMT promoter methylation status, and provides an overview of the advantages, limitations, and requirements of different assays. The importance of molecular diagnostic testing in neuro-oncology is emphasized, along with discussions on clinical relevance, accessibility, cost, and ethical aspects.