PDCD1 and neoplasm: PD-1: programmed cell death protein-1; PD-L1: programmed death-ligand 1; MSI-H: microsatellite instability-high; dMMR: deficient mismatch repair; LDH: lactate dehydrogenase; CTLA-4: cytotoxic T-lymphocyte-associated protein 4; REC: relative eosinophil count; S100B: S100 calcium-binding protein B; HER2: human epidermal growth factor receptor 2; TILs: tumor-infiltrating lymphocytes; ctDNA: circulating tumor DNA; TMB: tumor mutational burden; NSCLC: non-small cell lung cancer; TNBC: triple-negative breast cancer; RCC: renal cell carcinoma; ICIs: immune checkpoint inhibitors