PECAM1 and breast cancer: Consistent with our previous report,[25] flow cytometry analysis of single cell suspensions isolated from human breast cancer (Figure 1A) and immunofluorescence staining of clinical samples (Figure 1B) revealed that CD10 in tumors was predominantly expressed by a subset of GPR77+ CAFs negative for the pan‐leukocyte marker CD45, and the epithelial cell adhesion molecule (EpCAM), and the endothelial cell markers CD31.