Indeed, correlating IDH-status with clinical and demographic parameters of GBM patients clearly indicated the existence of two distinct clinicopathologic entities: (1) those tumors that tend to arise in younger patients as lower-grade astrocytomas and progress over time to GBM-IDH-mutant versus (2) those that tend to arise in older patients and more rapidly lead to death, namely GBM-IDH-wild type. This evidence concerns the gene IDH1 and glioblastoma.