CD33 and breast cancer: eMDSCs are a newly defined subset of MDSCs, whose phenotype in breast cancer were defined as Lin−HLA-DR-CD45+CD33+CD13+CD14−CD15− in humans and CD11b+Gr-1-F4/80-MHC-II- in mice (Zhou et al., 2010; Yu et al., 2013; Yu et al., 2014; Jiang et al., 2017; Zhang et al., 2018).