While the term glioblastoma is only used for IDH wildtype gliomas and no longer for IDH-mutated gliomas, the term astrocytoma Grade 4 is newly introduced for IDH-mutated gliomas with features of high malignant behavior (i.e., mitoses, microvascular proliferation, and necrosis) without 1p/19q loss. The gene discussed is IDH2; the disease is central nervous system cancer.