Updated project metadata. Post translational spliced peptides bound to the HLA are unique type of peptides, shown in cancer, for HLA-class-I. Thus far, no consensus has been reached on the extent to which post-translational spliced peptides (PTSPs) occur, stirring significant debate. Furthermore, the role of the HLA-class-II pathway has been studied only in diabetes. Here, we exploit our large-scale cancer peptidomics database and devise a pipeline to filter spliced peptide predictions, to identify recurring spliced peptides, both for HLA-class-I and -II. Our results indicate that HLA-Class-I spliced peptides account for a low percentage (4.4%) of the immunopeptidome, yet are larger in number relative to other types of identified aberrant peptides. Therefore, spliced peptides contribute significantly to the repertoire of presented peptides in cancer cells. In addition, HLA-class-II bound spliced peptides were identified as well, but to a lower extent (0.6%).