CD33 and pancreatic intraductal papillary-mucinous neoplasm: Since human myeloid-derived suppressor cells have an immunophenotype CD11b+CD33+HLA-DR− (Gabrilovich and Nagaraj, 2009), we supplemented the immunohistochemistry with CD33 and HLA-DR antibodies, and our results confirmed the presence of MDSCs in IPMN tissues.