Low-grade IDH-mutant gliomas (LGGs) are low-cell-density, diffusely infiltrating, and slow-growing tumours, composed of well-differentiated glial (astrocytic or oligodendroglial) cells, with mild nuclear atypia and a lack of mitosis, necrosis, or microvascular proliferation [79,80]. The gene discussed is IDH2; the disease is glioma.