CD8A and cancer: An increased number of tumor-infiltrating cytotoxic T-lymphocytes (CD8+) in MSI compared with MSS tumors for both the tumor and peritumoral area. Quantification showed high numbers of intra-epithelial CD3+, CD4+, CD8+, CD20+ and CD68+ cells in MSI compared with MSS cancers (all p <= 0.01).