A Case with Ga-FAPI Positive and F-FDG Negative Breast Cancer.

A female patient diagnosed of infiltrative breast carcinoma using tru-cut biopsy underwent flourine-fluorodeoxyglucose (F-FDG) positron emission tomography/computed tomography (PET/CT) for staging. The tumor was located in the superior external quadrant of the right breast, and did not exhibit pathological uptake in F-FDG PET/CT. Later, gallium- (Ga) fibroblast activation protein-specific inhibitor (FAPI)-04 PET/CT imaging was performed and the primary tumor showed intense radiotracer accumulation. This presumes that Ga-FAPI PET/CT imaging is superior to F-FDG imaging in detecting the primary tumor in breast cancer, thereby suggesting the replacement of FAPI by F-FDG in breast-cancer staging in the future.