PDPN and breast cancer: The prognostic value of CECs expressing different types of surface or intracellular proteins such as the epithelial cell surface marker epithelial cell adhesion molecule (EpCAM), the lymphatic endothelial cell maker podoplanin (PDPN) and the epithelial-mesenchymal transition (EMT) marker vimentin has been found in head and neck cancer, colorectal cancer, breast cancer, prostate cancer and lung cancer [19–26].