S100A4 and neoplasm: CAFs are often characterized by elevated expression of markers such as alpha-Smooth Muscle Actin (αSMA), fibroblast activation protein (FAP), fibroblast-specific protein 1 (FSP1 or S100A4), Vimentin, CD90 (Thy-1), podoplanin, platelet-derived growth factor receptor-α (PDGFRα), and/or PDGFRβ, which are present in various combinations across different types of tumor and play different pro-tumorgenic functions [26,27,28].