In 2020, a study conducted by Karimi and colleagues investigated PD-L1 expression in a cohort of 93 meningiomas (n = 41 WHO°1, n = 43 WHO°2 and n = 9 WHO°3) using IHC in whole-tissue sections and reported PD-L1 positivity in 43% of all cases, with a significantly increased PD-L1 expression in higher-grade tumors. This evidence concerns the gene CD274 and meningioma.