METHODS: Fresh tumor tissue, paired non-tumor liver tissue, and peripheral blood samples from 93 patients with HCC were analyzed using multiparametric flow cytometry to characterize lymphocyte subsets (T cells, NK cells, NKT cells, and B cells), immune checkpoint molecule expression (ICOS, 4-1BB, OX40, PD-1, TIM-3, LAG-3, and CTLA-4), and activation status. The gene discussed is ICOS; the disease is neoplasm.