Patients ≥ 55 years at diagnosis with no immunoreactivity for IDH1 R132H can be diagnosed as glioblastoma IDH-wildtype CNS WHO grade 4 if histopathological features of glioblastomas are present, the tumour is not located in the midline and there is no history of earlier low-grade glioma [26]. Here, IDH1 is linked to glioblastoma.