According to recent discoveries, GBMs are now subdivided based on the mutational state of isocitrate dehydrogenase (IDH) genes in IDH wild type which corresponds most frequently with the clinically defined primary or de novo GBM, IDH mutant which corresponds to the so-called secondary GBM, and those not otherwise specified (NOS) for which the IDH status could not be determined [17]. The gene discussed is IDH1; the disease is glioblastoma.