Revision of the Histopathological Examination Following ⁶⁸Ga-DOTA-FAPI-04 PET/CT of a Breast Tumor Diagnosed as Invasive Ductal Carcinomatosis

Neuroendocrine tumors (NETs) of the breast represent 1% of breast carcinomas. Histopathological misinterpretation of breast NET is common. We present the case of a female patient who had a breast mass diagnosed as invasive ductal carcinoma initially by histopathological examination. Fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) revealed 2 ametabolic hypodense liver lesions. Subsequently, the patient underwent fibroblast activation protein inhibitor (FAPI)-PET/CT, which did not reveal any FAP expression in the liver lesions, but increased FAP expression was observed in the soft tissue mass of the mesenteric root. Consequently, the pathology of the biopsy taken from the nodule in the right breast was revised, and a diagnosis of grade 2 NET was established. The benefit of FAPI-PET/CT on NETs has been previously investigated. Further prospective studies are required to establish the role of FAPI-PET/CT in NET management.