PIK3CA and meningioma: TRAF-7 mutated meningiomas demonstrated elevated levels of programmed death ligand-1 (PD-L1), the major ligand for the programmed death checkpoint pathway, while PD-L2 is highly expressed in PI3K/AKT/mTOR pathway mutations and CTLA-4 was frequently expressed in PIK3CA and SMO mutated tumors.