HLA-S and neoplasm: On the basis of the expression patterns of the HLAs, tumor antigens can be classified into two general groups: tumor-associated antigens (TAAs), in which the antigen is presented by the HLAs that are only expressed on tumor cells (mainly HLA class I), and tumor-specific antigens (TSAs, or neoantigens), in which the antigen is presented by the HLAs that are expressed not only on cancer cells, but also to normal cells [28,92].