Updating the grading criteria for adult diffuse gliomas: beyond the WHO2016CNS classification

Excerpt

The classification of adult diffuse gliomas has shifted from the traditional histogenetic classification to a molecular one in the updated 4th edition of the WHO Classification of Tumours of the Central Nervous System, published in 2016 (WHO2016CNS) [10]. This shift is based on the discovery of isocitrate dehydrogenase (IDH) mutations as the most upstream genetic event in two canonical diffuse glioma lineages: diffuse astrocytomas and oligodendrogliomas of adults (the “molecular era”) [7, 8]. While this revision represents a paradigm shift in brain tumor classification, the grading schemes for diffuse gliomas were not modified simultaneously, as no alternative method that satisfactorily replaces the traditional histological grading approach using morphologic features (i.e. anaplasia, mitosis, microvascular proliferation [MVP] and necrosis has yet been reported). …