This phenomenon of acquired somatic hypermutation following temozolomide treatment has been documented in several glioma types including IDH-mutant astrocytomas, IDH-mutant and 1p/19q-codeleted oligodendrogliomas, IDH-wildtype glioblastomas, and histone H3 G34-mutant diffuse hemispheric gliomas [12, 41, 46, 49, 50]. The gene discussed is IDH1; the disease is oligodendroglioma.