PD‐L1 expression pattern as predictive factor of biological behaviour in intracranial meningiomas: A single‐center retrospective study

Background: Molecular expression of meningiomas has become increasingly important for predicting their biological behaviour. However, the factors influencing tumour recurrence and progression after surgery remain unclear. Recent studies suggest that programmed death-ligand 1 (PD-L1) could be a key predictive and therapeutic factor in these tumours. Methods: This single-center retrospective study included 96 patients who underwent Simpson Grade I resection of intracranial meningiomas between 2001 and 2022. PD-L1 expression was assessed immunohistochemically (clone SP142) and categorized as overall (OE), membranous (mb), granular cytoplasmic (gr) and perinuclear dot-like. Associations with WHO grade, recurrence, mitotic count and Ki-67 index were analysed using univariate and multivariate statistics. Results: 118 samples were analysed. Grade 2 meningiomas showed significantly higher mitotic count (4.0 ± 5.5 vs. 1.0 ± 1.0 n/mm2, p < .001) and Ki-67 index (7.6 ± 2.1% vs. 3.5 ± .2%, p < .001) than Grade 1. PD-L1 OE (2.0 ± 5.0% vs. .0 ± 1.0%, p < .001), gr (1.0 ± 2.5% vs. .0 ± 1.0%, p < .001) and mb (1.0 ± 1.0% vs. .0 ± .0%, p = .003) expressions were also higher in Grade 2. At recurrence, Grade 1 tumours progressing to Grade 2 showed increased PD-L1 OE (p = .025), gr (p = .024) and mb (p = .037). Multivariate analysis confirmed PD-L1 gr and mb as independent markers of high-grade tumours. Conclusions: Granular cytoplasmic and membranous PD-L1 expression patterns are significantly associated with tumour grade, recurrence and progression, suggesting their potential role as prognostic biomarkers in meningiomas.