The decision forthis grouping is according to the most recent (2021) WHO grading14 and current state of the art in histopathologicalpractice,23 where gliomas are groupedmolecularly based on their isocitrate dehydrogenase (IDH) and 1p/19q status so that grade4 glioblastomas (IDH-wildtype) are defined as higher grade and clearly separated from thebiologically and clinically more benign IDH-mutant, and 1p/19q-codeleted, lower gradegliomas (defined as WHO grades 2 and 3). The gene discussed is IDH3A; the disease is central nervous system cancer.