PDPN and bone metastasis: Immunohistochemical staining was used to evaluate the expression of CAF related proteins (podoplanin, prolyl 4-hydroxylase, FAPα, S100A4, PDGFRα, PDGFRβ, and NG2) in tissue microarrays from 132 cases of metastatic breast cancer (bone metastasis: 32 cases, brain metastasis: 38 cases, liver metastasis: 10 cases, and lung metastasis: 52 cases).