Programmed death‐ligand 1 (PD‐L1) expression in pleomorphic carcinoma of the lung

Background and Objectives Pulmonary pleomorphic carcinoma (PPC) is a rare and aggressive subtype of lung cancer. Programmed cell death‐ligand 1 (PD‐L1) expression may be induced in a variety of malignant tumors, but its prognostic implication in PPC remains unclear. Methods Twenty‐six patients with surgically resected PPC were retrospectively reviewed. Immuno‐histochemical staining was used to detect PD‐L1 expression, and PD‐L1 status was classified into “high” or “low” according to the percentage of tumor cells (TCs) expressing PD‐L1 (tumor proportion score, TPS). Results PD‐L1 expression was positive in 20 (76.9%) patients at the cut‐off TPS value of 1%. A receiver‐operating characteristic (ROC) analysis showed that the optimal cut‐off value was 15% for prediction of cancer‐specific death with the area under ROC curve of 0.701 (P = 0.107). High PD‐L1 expression was associated with a favorable overall survival (100% vs 45.9% at 5 years; P = 0.046) as well as a favorable cancer‐specific survival (88.9% vs 37.5% at 5 years; P = 0.012). A multivariate analysis indicated a trend toward a favorable prognosis associated with high PD‐L1 expression (hazard ratio [HR], 0.254 [95% confidence interval, 0.054‐1.200]; P = 0.084). Conclusions PD‐L1 expression was positive in most PPC cases, and high PD‐L1 expression may predict a favorable prognosis in resected PPC.