IDH1 and oligodendroglioma: Here, diffuse gliomas (LGG) are subdivided partly based upon molecular markers into: astrocytomas, IDH-mutated tumors without 1p/19q co-deletion, oligodendrogliomas, IDH-mutated tumors with a 1p/19q-codeletion, and IDH-wildtype astrocytomas (WHO 2021 5th edition).