Common and clinically relevant genetic subtypes include gliomas with mutations of the isocitrate dehydrogenase (IDH) genes 1 or 2 with or without chromosome 1p and 19q (1p/19q) codeletion.5 Within most neuropathology laboratories, 1p/19q-codeletion is established using the cytogenetic technique of fluorescence in-situ hybridization (FISH). Here, IDH2 is linked to central nervous system cancer.