As of the 2016 revised 4th edition of the WHO Classification of Tumours of the Central Nervous System, classification of diffuse gliomas involves consideration of both histopathologic features as well as molecular and genetic features, including 1p/19q codeletion status and mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2). This evidence concerns the gene IDH1 and neoplasm.