Immunohistochemically, the brain tumor stained positive for epithelial membrane antigen (EMA), progesterone receptor (PR), vimentin, and E-cadherin (Fig. 2B) and negative for glial fibrillary acidic protein (GFAP), S-100, p53, and oligodendrocyte transcription factor 2 (Olig2), which was consistent with WHO grade I meningioma. The gene discussed is OLIG2; the disease is meningioma.