This study was designed to evaluate the immunohistochemical expression of programmed death ligand-1 (PD-L1) in tumor cells (TCs) and tumor-infiltrating immune cells (TICs) in hepatocellular carcinoma (HCC) and to correlate its expression with clinicopathological parameters. Seventy-two formalin-fixed paraffin-embedded blocks of HCC were collected. The data were collected from the patients' records. The blocks were stained with hematoxylin and eosin. Additionally, they were immunostained with PD-L1. Membranous staining was considered positive expression including the entire membrane or part of it ± cytoplasmic staining, and the percentage of total cancer cells ≥ 5% was evaluated as positive staining for TCs. The TICs were considered positive if they expressed membranous ± cytoplasmic staining of PD-L1 ≥ 1%. Of the total cases, 34.7% expressed PD-L1 positively in TCs and 15.3% expressed PD-L1 positively in TICs. Significant associations were observed between PD-L1 expression in TCs and tumor grade, capsular and/or vascular invasion, tumor stage, nodal metastasis, and the expression of PD-L1 in paracancerous tissue. The cases that positively expressed PD-L1 exhibited reduced overall survival (OS). PD-L1 was expressed in HCC TCs and TICs. Its expression in TCs was associated with higher HCC grades, advanced stages, capsular and/or vascular invasion, and nodal metastasis, and cases that expressed PD-L1 displayed reduced OS. Therefore, PD-L1 might serve as a poor prognostic indicator and a tumor immunotherapy target.
Keywords: Hepatocellular carcinoma; PD-L1; prognosis; tumor cells; tumor-infiltrating cells.