False-Positive FAPI Expression in Benign Breast Adenosis

Abstract Breast adenosis is a benign glandular proliferative disorder. Due to its imaging similarities with other malignant breast lesions, differentiating adenosis from other invasive carcinomas of the breast poses a diagnostic challenge. Fibroblast activation protein inhibitor (FAPI) expression is observed in various benign and malignant lesions, increasing the risk of false-positive results. We present a case of FAPI-avid benign breast adenosis in a patient with adrenal adenocarcinoma in 68 Ga-FAPI-46 PET/CT.