IDH1 and glioblastoma: Glioblastoma (GBM) WHO grade IV is the most frequent and malignant primary tumor of the Central Nervous System (CNS) associated with significant morbidity, mortality, and treatment resistance.1 Under the 2016 World Health Organization Classification of Tumors of the Central Nervous System, the 3 recognized morphological variants of IDH-wildtype (IDHwt) GBM are giant cell GBM (gcGBM), gliosarcoma, and epitheloid GBM.2