The current World Health Organisation classification for CNS tumors recommends integrated diagnosis based on combined phenotypic and genotypic findings [1] Although originating from common progenitor cells harboring Isocitrate Dehydrogenase (NADP(+)) (IDH) mutations, oligodendrogliomas differ from diffuse astrocytomas by combined whole-arm losses of chromosome 1p and 19q (1p/19q codeletion) and frequent Telomerase Reverse Transcriptase (TERT) promoter mutations. The gene discussed is IDH1; the disease is oligodendroglioma.