PDPN and breast cancer: Immunohistochemical analysis on human breast cancer tissues further revealed distinct expression patterns of fibroblast markers in CAFs at different metastatic sites [32]: high expression levels of podoplanin, S100A4, and PDGF-Rα in bone metastasis sites, high expression levels of PDGF-Rβ in lung metastasis sites, and reduced expression levels of S100A4 and PDGF-Rα in liver metastasis sites.