Depleted and dysfunctional tumor-infiltrating lymphocytes (TILs) in HNC cases are characterized by upregulation of several checkpoint markers, such as programmed cell death 1 (PD-1), lymphocyte-activating gene 3 (LAG-3), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) [21]. The gene discussed is PDCD1; the disease is neoplasm.