POLR2A and meningioma: The number of patients harboring each mutation based on pathological diagnosis is indicated in a bar graph in Fig. 4A. AKT1, KLF4, SMO, or POLR2A mutation was significantly more frequent in WHO grade I meningioma than in WHO grade II meningioma (p = 0.01) (Fig. 4B), and any one of these four mutations was more frequently associated with meningothelial histological types than with other pathological types.