S100A4 and neoplasm: In human and mouse PDA, researchers found that common fibroblast markers such as αSMA, podoplanin, platelet-derived growth factor receptor Alpha/Beta (PDGFRα/β), fibroblast specific protein 1 (FSP1), fibroblast activating protein (FAP), and desmin varied in their staining intensity, distribution, and overlap throughout the tumor tissue [6,26,99,111,116,117,118,119].