CD38 and neoplasm: Taken together, despite the universal decreasing tendency of cytotoxicity and cytokine secretion of CD38+ CD8+ T cells and CD38− CD8+ T cells in tumor compared with normal tissue, our results found that tumor-infiltrating CD38+ CD8+ T cells are advantages in cytotoxicity, cytokine secretion and tumor-killing ability than tumor-infiltrating CD38− CD8+ T cells in the natural condition which may result from pre-activation.