CD274 and hepatocellular carcinoma: Serum PD-L1 levels did not correlate significantly to HCC etiology (Mann–Whitney U test, p = 0.732), Child–Pugh score (Kruskal–Wallis test, p = 0.488) and HCC stage (Kruskal–Wallis test, p = 0.063) probably due to the small number of patients with detectable sPD-L1.