TNF and meningioma: Tumor-infiltrating macrophages could produce TNF-α to increase PD-L1 expression on tumor cells and stabilize PD-L1 via the NF-κB pathway.30 The conspicuous macrophage infiltration in LPRM may induce PD-L1 overexpression of meningioma cells, as demonstrated in our case unless a clear influence on tumor aggressiveness.