IDH1 and astrocytoma (excluding glioblastoma): In principle, grade IV astrocytomas almost invariably carry IDH1/2 mutations, while glioblastoma is always IDH wild type; secondly, the presence of either TERT promoter mutation or EGFR gene amplification, as well as chromosome 7 gain along with chromosome 10 loss qualify astrocytic gliomas as a glioblastoma, even when some histological markers of malignancy are absent.