CD274 and breast cancer: In the present study, we found that PD-L1 was preferentially expressed in CD16 + Mo, Mo/Mφ, MDSC, mDC, DC, and the percentages of the PD-L1 positive cells of these lineages were significantly higher in tumor tissues than in blood, suggesting that these fractions are involved primarily in the PD-L1 pathway in breast cancer tissue.