Subsequent genetic discoveries on the loss of heterozygosity in chromosomes 1p and 19q from the majority of oligodendroglioma patients [2, 17] as well as immunohistochemical studies showing differential expression of Olig2 [20, 21] and synaptophysin [3, 11, 22] in oligodendroglioma and central neurocytoma, respectively, have greatly helped the diagnosis. This evidence concerns the gene OLIG2 and oligodendroglioma.