A High PD-L1 Expression in Pulmonary Pleomorphic Carcinoma Correlates with Parietal-pleural Invasion and Might Predict a Poor Prognosis.

Objective Pleomorphic carcinoma (PC) is a rare pulmonary epithelial malignant tumor with a poor prognosis. The objective of the present study was to investigate the programmed death-ligand 1 (PD-L1) expression in PC and its correlation between the clinicopathological factors and prognosis. Methods Clinical and pathological data of 35 patients with surgically resected PC encountered from 2002 to 2016 at our institution were collected. The PD-L1 expression on tumor cells was evaluated via immunohistochemistry (clone 22C3). We examined the correlation between the PD-L1 expression and patients' clinicopathological factors and their prognosis. Results A high PD-L1 expression (≥50%) was seen in 21 (60%) patients, and parietal-pleural invasion was significantly correlated with a high PD-L1 expression (p=0.012). The 5-year overall survival and relapse-free survival were 68.2% and 43.2%, respectively. Tumor size ≥50 mm (p=0.021), lymph node metastasis (p=0.023), and a high PD-L1 expression (p=0.047) were correlated with a short relapse-free survival. Since lymph node metastasis was an independent risk factor of a poor overall survival (p=0.012), patients with a high PD-L1 expression also tended to have a worse overall survival than those with low levels (p=0.081). Conclusion A high PD-L1 expression is frequently seen in PC. The PD-L1 expression is associated with parietal-pleural invasion and might indicate a poor prognosis.