PDCD1 and hepatocellular carcinoma: Studies in the literature have shown the importance of overexpression of immune checkpoints like programmed cell death 1 (PD-1), cytotoxic T-lymphocyte antigen 4 (CTLA-4), lymphocyte activating gene 3 protein (LAG-3), and mucin domain molecule 3 (TIM-3), which leads to HCC development [8].