Recently, studies have suggested that at least genetically, the majority of these “mixed histology” tumors contain genetic events representative of either astrocytomas, namely mutations in IDH1, ATRX, and TP53, or oligodendrogliomas, namely chr 1p/19q LOH and mutations in CIC and/or FUBP1 [9, 11, 18, 19]. The gene discussed is ATRX; the disease is oligodendroglioma.