CTSS and neoplasm: These data show for the first time that by altering the processing of antigenic peptides, CTSS mutations or overexpression remodel the immune microenvironment to promote lymphoma growth and implies that targeting a regulator of antigen presentation such as CTSS could modulate the spectrum of processed antigens, promote activation of cytotoxic T cells, enhance tumor immunogenicity and improve response to anti-PD1 immunotherapies.