IDH1 and oligodendroglioma: According to the 2007 WHO classification, oligodendrogliomas could be diagnosed only when typical histological features are associated with the recently defined “oligodendroglioma, IDH-mutant and 1p/19q codeleted”, a molecular condition that requires the concomitancy of both IDH1 or IDH2 mutations and 1p/19q co-deletion.