Although some studies have recently called the role of histologic features into question, in IDH-mutant 1p/19q co-deleted oligodendrogliomas histologic features remain an important prognostic factor with increased mitotic figures, microvascular proliferation (MVP), and necrosis dividing grade II from grade III [33,92,99,100,101]. This evidence concerns the gene IDH1 and oligodendroglioma.