In the 2021 WHO CNS, glioblastoma is defined as a tumor with obligatory wildtype IDH1/2, characterized by diffuse astrocytic histology and at least one of the following features: necrosis, microvascular proliferation, gain of chr 7 and loss of chr 10, EGFR amplification, or TERT mutation [27]. Here, IDH1 is linked to neoplasm.