In the context of tumor development, the expression levels of NKG2A and NKG2C reflect the inhibition or activation status of NK cells [1, 4, 71-73], thereby providing useful indicators for studying the regulatory mechanisms of NK cells; however, the function of NKG2A and NKG2C is dependent on the expression of their ligands, such as HLA-E molecules, which may be affected by a variety of factors, thereby limiting the analyses based on these markers [38, 74]. This evidence concerns the gene KLRC2 and neoplasm.