CD8A and malignant colon neoplasm: The peritoneal cavity is an immunologically unique compartment.1–5 It has distinct immunological features, in comparison to systemic immunity, with relatively abundant dendritic cells (DCs), predominant CD8+ T cells over CD4+ T cells, and abundant soluble factors in peritoneal fluids, which establishes a robust immune competency.4 6 However, cancer cells can nullify this peritoneal immunity through various immune evasive mechanisms, and rapidly metastasize into the peritoneal cavity, making it the second most common site of metastasis in patients with colon cancer.1 3 6–9