CD8A and breast cancer: While one study demonstrated that both the total number and the distant stromal (more than one tumor cell diameter of the tumor) CD8+ CTLs significantly associated with better prognosis of breast cancer and its subtypes (ER negative cancer, HER-2 negative cancer and basal-like cancer) [25], another study showed that neither intratumoral (within tumor cell nests) nor peritumoral (stroma without direct contact with the cancer cells) CD8+ CTLs had protective effect on survival of breast cancer patients [26].