S100A4 and breast cancer: analyzed 132 specimens of breast cancer metastases by immunohistochemistry and found that the expression of CAF-related proteins in the stroma varies with the location of breast cancer metastasis: in lung metastasis, PDGFRα is highly expressed; in liver metastasis, S100A4 and PDGFRα have low expression; and in bone metastasis, podoplanin, S100A4, and PDGFRα are highly expressed (32).