ACTA1 and neoplasm: To investigate whether 68Ga-FAPI PET/CT imaging can reflect tumor CAF subtypes in vivo, we stained metastatic CRC tumors that were detected by 68Ga-FAPI PET/CT or 18F-FDG PET/CT scan with α-smooth muscle actin (α-SMA), a marker for myofibroblastic CAFs (myCAFs) (47), and PDGFRA, a marker for the inflammatory subtype of CAFs (iCAFs) (48).