MKI67 and neoplasm: Immunohistochemical (IHC) studies demonstrated strong GFAP and OLIG2 staining, approximately 50% MIB-1/Ki-67 proliferation index, frequent nuclear p53 staining, loss of p16 staining, intact ATRX expression, and largely negative IDH1 R132H expression, although scattered cells demonstrated positive cytoplasmic expression (<1% of total tumor cells) (Figure 1).