In addition, differences in tumour biology, such as higher prevalence of IDH mutations in glioblastomas of younger as compared to older patients, might contribute to prognostic differences, in particular in studies that did not stratify according to IDH mutation status (Eckel-Passow et al. 2015; Hartmann et al. 2010; Houillier et al. 2010; Parsons et al. 2008). The gene discussed is IDH1; the disease is neoplasm.