IDH1 and oligodendroglioma: Recently, the 2021 version of the World Health Organization (WHO) Classification of tumors in the central nervous system further emphasized the molecular aspects of the classification, where adult-type dLGGs are characterized by the IDH-mutation [2] Moreover, due to the controversy of WHO-grading within the IDH-mutated tumors, it is now more common to report diffuse grade 2 and 3 astrocytomas (IDH-mutant without 1p19q codeletion) and oligodendrogliomas (IDH-mutant with 1p19q-codeletion) together under the term lower-grade gliomas [3,4].