Typical immunohistochemistry reactions of a GBM (Case #13). H and E stained section shows a hypercellular tumor (A). Immunohistochemistry reaction for GFAP (B) shows many positive processes in the background, but most tumor cells appear negative. This tumor is thus graded as showing LOW expression of GFAP. Stains for OXCT1 (C) show that most tumor cells are negative, with rare (less than 5%) cells (possibly entrapped native neurons) showing positive reaction (shown at higher magnification in the inset). Most cells also appear negative for BDH1 (D), but more than 20% of cells appear positive for BDH2 (E). A little more than 5% of tumor cells appear positive for ACAT1 (F) (shown at higher magnification in the inset). More than 20% of tumor cells are positive for the glycolytic enzymes HK2 (G) and PKM2 (H).