SMO and meningioma: A second study by Brastianos et al. showed: the occurrence of NF2 mutations in 43% of meningiomas, this mutation being more frequent among grade II than grade I tumors; alterations in genetic modifiers observed in 8% of meningiomas, particularly in grade III tumors; a subset of meningiomas lacking NF2 mutations, harboring recurrent oncogenic mutations in AKT1 and SMO and showing evidence of activation of these pathways [205].