IDH2 and oligodendroglioma: Bianconi et al. [14], in a retrospective cohort of 112 patients with IDH-mutant lower-grade gliomas (astrocytomas and oligodendrogliomas, WHO grades 2–3), reported intraoperative 5-ALA-induced fluorescence in 25% of grade 2 and 43% of grade 3 tumors.