Introduction to WHO Classification of Tumors of the Central Nervous System, 2016

Abstract

The World Health Organization classification (WHO) of CNS tumors is considered a gold standard and followed worldwide. The previous version (2007) of WHO classification of CNS tumors was epicentered on histological features of the tumor [hematoxylin–eosin staining (HE)], immunohistochemical (IHC) lineage-associated proteins, and ultrastructural characteristics with different putative cells of origin and level of differentiation. 2016 WHO classification update includes both phenotypic and genotypic parameters, making it more objective than the previous classification. In the past few decades, extensive evolvement of molecular studies followed by clinically proven trials provided a prognostic and a predictive data within diagnostic categories. In 2014, a meeting was held in Haarlem, the Netherlands, by the International Society of Neuropathology to formulate and incorporate the molecular findings into CNS tumor classification and diagnosis. This meeting was attended by 117 eminent contributors from 20 countries. Finally, the WHO classification of CNS tumors was updated in 2016 based on histological classification, the grade, and molecular information.

The WHO 2016 classification of CNS tumors implemented new nomenclature, WHO grades, their molecular genetics profile, the addition of newer entities along with the omission of certain entities.