IDH1 and glioma: According to the WHO CNS5 classification, complemented by the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy (cIMPACT-NOW), IDH-mutated gliomas can be further subdivided into astrocytomas (grade 2, 3, or 4) and oligodendrogliomas with 1p/19q codeletion status (grade 2 or 3) [12,14,15] (Figure 1).