IDH1 and oligodendroglioma: This classification system includes five main categories of adult diffuse glioma: glioblastoma, IDH-wild type; glioblastoma, IDH-mutant; diffuse or anaplastic astrocytoma, IDH-wild type; Diffuse or anaplastic astrocytoma, IDH-mutant, and oligodendroglioma or anaplastic oligodendroglioma, IDH-mutant, and 1p19q co-deletion.