Oligodendrogliomas are rare tumours accounting for 2–3% of primary CNS tumours.1 The current 2021 WHO classification of CNS tumours (fifth edition) is built on the previous edition, published in 2016 (revised fourth edition), which for the first time incorporated molecular parameters in addition to the histopathologic appearance to obtain the diagnosis of brain tumours.2,3 To establish the diagnosis of oligodendroglioma, the 2021 WHO classification (and the revised fourth edition of 2016) requires the presence of both isocitrate dehydrogenase (IDH) mutations and 1p/19q codeletion. Here, IDH3A is linked to oligodendroglioma.