S100A4 and invasive ductal breast carcinoma: An IHC-based study by Koo et al. [159] showed high levels of FAP-α, FSP-1/S100A4, and PDGFR-β in the stroma, and expression of FAP-α and FSP-1/S100A4 was higher in both tumor and stromal cells compared to invasive ductal carcinoma.