The serine protease fibroblast activation protein (FAP) is a membrane-anchored enzyme which is specifically expressed in fibroblasts activated to differentiate to (proto-)myofibroblasts, but not in dormant fibroblasts or mature fibrocytes.568Gallium-labeled FAP-inhibitor (FAPI) compound 04 (68Ga-FAPI-04) was initially introduced for PET imaging of cancer-associated fibroblasts.6 In our previous work, we demonstrated that image derived FAP expression after MI in a rat model allowed noninvasive PET imaging of activated fibroblasts.7 The gene discussed is FAP; the disease is cancer.