Pathology and Genetics of Gliomas

Current World Health Organization (WHO) classification of the neuroepithelial tumors is cell lineage-oriented and based on a presumed developmental tree of the central nervous system (CNS). It defines three main groups of gliomas, namely astrocytomas, oligodendrogliomas, and ependymomas, and additionally presumes their 4-tiered histopathological grading (WHO grades I to IV). Nevertheless, the impact of tumor pathology on clinically related parameters may be frequently much better predicted by genetics, than by histological appearance of the lesion. Recent studies have revealed several major molecular alterations typical for different types of neoplasms, such as IDH1/IDH2 mutations in diffusely infiltrating gliomas, mutations of TP53 and ATRX in astrocytomas, 1p/19q co-deletion in oligodendrogliomas, mutations of TERT promoter in oligodendrogliomas and IDH wild-type glioblastomas, and mutations or fusions of BRAF in circumscribed astrocytomas, particularly in children. Identification of those and several other genetic abnormalities in the tumor is clinically important and may help clinicians to determine proper treatment strategy and to predict prognosis. Therefore, the updated WHO classification of CNS tumors (2016) considers not only phenotype, but also some genetic characteristics of gliomas.