PDCD1 and head and neck squamous cell carcinoma: Consistent with findings in TCGA HNSCC patients of PIK3CAAmp/TP53Mutated cohort, we found KPPA tumors harbored a low level of CD8 TILs that expressed a higher level of PD-1 and exhibited reduced polyfunctionality, suggesting that these CD8 TILs were chronically activated and experienced exhaustion.