According to the 2021 update of the WHO Classification of Central Nervous System (CNS) Tumors, the categorization of tumors previously referred to as glioblastoma was modified to include two diagnoses based on the presence or absence of IDH mutation [4]: (i) glioblastoma, IDH-wildtype, CNS WHO grade 4 and (ii) astrocytoma, IDH-mutant, CNS WHO grade 4. The gene discussed is IDH2; the disease is glioblastoma.