Moreover, >99% of the cells were negative for the epithelial cell adhesion molecule (EpCAM), a breast cancer epithelial cell surface marker[12]; CD31, also known as platelet endothelial cell adhesion molecule (PECAM-1), an endothelial cell marker, and CD45, a pan-leukocyte marker (Figure 2, lower panel). This evidence concerns the gene PTPRC and breast cancer.