Prevalence of High Programmed Death-Ligand 1 Expression in Pulmonary Sarcomatoid Carcinoma: A Systematic Review and Meta-Analysis.

Pulmonary sarcomatoid carcinoma (PSC) is a rare, aggressive variant of NSCLC associated with emerging evidence of high programmed death-ligand 1 (PD-L1) expression, although its reported prevalence varies widely. We conducted a systematic review and meta-analysis to quantify the pooled prevalence of PD-L1 expression in PSC and identify factors associated with its variability. We searched PubMed, Web of Science, and the Cochrane Library up to November 2025. Studies reporting PD-L1 expression using the tumor proportion score (TPS) in confirmed PSC (≥ 10 patients) were included. A random-effects meta-analysis was performed for TPS thresholds of 50% and 1%. Subgroup analyses and meta-regression were used to explore sources of heterogeneity. This study was registered with PROSPERO (CRD420251243606). Thirty-four studies, encompassing up to 1789 patients, were included. The pooled prevalence of high PD-L1 expression (TPS ≥ 50%) was 57.33%, and PD-L1 positivity (TPS ≥ 1%) was 79.61%. At a TPS of 50% or higher, non-Asian studies reported a numerically higher prevalence than Asian studies, although the difference was not statistically significant. A higher proportion of ever-smokers and a 100% pleomorphic carcinoma composition were each associated with a significantly higher prevalence at a TPS of 1% or higher. In the meta-regression, no covariate reached statistical significance at a TPS of 50% or higher, whereas the proportions of pleomorphic carcinoma, ever-smokers, and median age were significant predictors at a TPS of 1% or higher. PD-L1 expression is remarkably prevalent in PSC, substantially exceeding that in conventional NSCLC. These findings may inform immunotherapy decision-making for advanced PSC.