PDCD1 and neoplasm: Furthermore, ligand-receptor analysis showed certain stronger interaction between high stemness malignant cells with immune cells in comparison to low stemness malignant cells, e.g., PDCD1-FAM3C pair, where FAM3C is noted to drive breast CSC formation [55], while PDCD1 expression is the marker of exhausted T cells and has a core role for tumor evasion from immune surveillance.