CAFs, the prominent stromal cell population in most types of human carcinomas, are α-SMA (alpha-smooth muscle actin) positive, spindle-shaped cells, which closely resemble normal myofibroblasts but express specific markers [i.e., FAP (fibroblast-associated protein), FSP-1 (fibroblast specific protein 1), and PDGFR-β (platelet-derived growth factor)] together with vimentin (a mesenchymal marker) and the absence of epithelial (cytokeratin, E-cadherin) and fully differentiated smooth muscle (smoothelin) markers (34–36). This evidence concerns the gene S100A4 and carcinoma.