In addition, the most recent WHO classification reserves the terminology of isocitrate dehydrogenase (IDH)-wild-type glioblastoma only for the cases of WHO grade 4 diffuse gliomas without IDH or histone H3 mutations, henceforth called glioblastomas, which represent approximately 90% of all WHO grade 4 diffuse gliomas. The gene discussed is IDH3A; the disease is glioblastoma.