IDH1 and oligodendroglioma: Therefore, from a clinical point of view, the three most common diffuse gliomas of adults should be distinguished: Glioblastoma IDH wild-type (which represents approximately 65–70% of adult glioma); Astrocytoma IDH mutant, 1p/19q non-codeleted (representing approximately 20–25%); and Oligodendroglioma IDH mutant, 1p/19q codeleted (5–7%) [1,5].