In light of the 2016 WHO classification update, GC is further subcategorized according to histopathologic grade and molecular findings, i.e., GC—diffuse astrocytoma, IDH-mutant; GC—diffuse astrocytoma, IDH-wildtype; GC—anaplastic astrocytoma, IDH-mutant; GC—anaplastic astrocytoma, IDH-wildtype; GC—glioblastoma, IDH-mutant; GC—glioblastoma, IDH-wildtype; GC—oligodendroglioma, IDH-mutant and 1p/19q-codeleted; GC—anaplastic oligodendroglioma, and IDH-mutant and 1p/19q-codeleted. The gene discussed is IDH1; the disease is oligodendroglioma.