Based on these characteristics of the tumor stroma, new radiotracers consisting of FAP-specific small molecule inhibitors (FAPI) have been developed for both tumor imaging and therapy, and their application has been described for imaging of various malignancies, including those that are not FDG-avid, and for showing a significantly high tumor-to-background contrast [4, 7–12]. The gene discussed is FAP; the disease is neoplasm.