Different subtypes of CAFs are characterized by distinct expression patterns of surface markers, such as fibroblast activation protein (FAP), α-SMA, fibroblast specific protein 1, platelet-derived growth factor receptor (PDGFR), etc. Of note, FAP has been recognized as a specific protein for CAFs, therefore FAP is frequently employed as a reliable marker to target CAFs in the process of cancer therapy or imaging diagnosis. Here, FAP is linked to cancer.