IDH1 and glioma: Over 70% of low-grade gliomas present mutations in IDH1 or IDH2. 15 On the contrary, only 5% of primary GBM are affected and 80% of secondary GBM have a mutated IDH1. 16 The last WHO classification version incorporates new entities to divide GBM into IDH-wild-type GBM (90% of cases that corresponds to primary GBM) and IDH-mutant GBM (10% of cases that corresponds to secondary GBM).2