Cytotoxic T lymphocytes (CD8+ CTL) are part of the adaptive immune system and induce tumor cell apoptosis through (1) recognition of antigens presented in the context of MHC class I leading to perforin/granzyme B secretion and (2) recognition of Fas on tumors via FasL, leading to caspase-mediated cell death. This evidence concerns the gene CD8A and neoplasm.