The concomitant presence of IDH1 mutation and 1p-19q co-deletion are classified as oligodendroglial variants, whereas neoplasms carrying IDH1 gene mutation in the absence of 1p-19q co-deletion are assigned to astrocytic forms, as well as tumor lesions with no evidence of IDH1 mutations (Prager et al, 2020; Van Den Bent et al, 2017; Caccese et al, 2020; Trautwein et al, 2022). The gene discussed is IDH1; the disease is neoplasm.