CD33 and colorectal cancer: To more detailed learn the dynamic change and clinical relevance of circulating and tumor-infiltrating Lin−/lowHLA-DR−CD11b+CD33+ MDSC in the colorectal cancer, in this study, we harvested the blood from 64 patients with varying stage of colorectal cancer and tumor and matched paraneoplastic tissues from 5 patients with stage III colorectal cancer, subjected them to multicolor flow cytmetric analysis of percentage, absolute number and phenotype of MDSC, and finally characterized their immunosuppressive functions.