A brief summary of the WHO 2021 classification of adult diffuse gliomas

Abstract The World Health Organization (WHO) classification system for central nervous system (CNS) tumors provides a distinct framework for differentiating these tumors from other types. Notably, gliomas are the most common and clinically significant primary brain tumors. The 2021 update of the WHO classification system (WHO CNS5), building upon the 2016 edition, integrates molecular genetics with histopathological insights to enhance diagnostic precision. This update advocates a multi-layered diagnostic strategy, combining histopathology, WHO grading, and molecular genetics into a unified diagnosis, thus refining the basis for clinical research, trials, and therapeutic interventions. In WHO CNS5, gliomas are categorized into three main groups based on IDH mutation and 1p/19q codeletion status: Diffuse astrocytoma with IDH-mutant, oligodendroglioma with IDH-mutant and 1p/19q-codeletion, and glioblastoma with IDH-wildtype. The diagnostic criteria for adult diffuse gliomas include detailed descriptions of the updated classification, focusing on the molecular markers and histopathological characteristics.