Endocrine Abstracts

Neuroendocrine tumors (NETs) of the breast are very rare. They represent less than 1% of breast carcinomas. It is important to differentiate metastatic neuroendocrine neoplasia from primary neuroendocrine neoplasia of the breast. Histopathological misinterpretation of a breast NET is common. In a study of 18 NET cases that metastasized to the breast, it was found that 62% of these tumors originated from the gastrointestinal tract and 28% from the lung. Forty-four percent of these tumors were incorrectly diagnosed as primary breast carcinoma We present you a case of a 59-year old female patient who visited the clinic due to occasional vomiting and nausea for the last year. Her examination revealed a breast mass, which had been initially diagnosed as Invasive Ductal Carcinoma by histopathological examination (Figure-1). After that, a Fluorodeoxyglucose (FDG) – Positron Emission Tomography (PET)/Computer Tomography (CT) was ordered to investigate the lesions. But the scan did not reveal any pathology. Subsequently, the patient underwent [68Galium (Ga)]Ga-Fibroblast Activation Protein Inhibitor (FAPI) PET/CT which demonstrated pathological uptake in the mesenteric root and breast (Figure 2-B). Due to the conflicting findings, histopathological examination of the tru-cut biopsy was repeated and it has confirmed the diagnosis of NET (Figure-3). Therefore, 68Ga-DOTATATE PET/CT was performed. Multiple lesions with increased DOTA activity were illustrated in bilateral breast, mesenteric root, bones and liver (Figure 2-C). Consequently, the revised diagnosis of grade 2 NET was confirmed by histopathology. Although the FAPI uptake pattern of NETs is not exactly established, heterogeneous uptake was reported. In addition to that, [68Ga]Ga-FAPI PET/CT’s utility in primary and metastatic NETs was previously demonstrated in case reports. It is also important to note that, although [68Ga]Ga-FAPI PET/CT has shown promising results in tumors of epithelial origin, these scans might be non-pathological depending on the tissue of NET. Our case demonstrates very useful information regarding unusual presentations of NETs. In the light of our case and previous research, we strongly believe that after further evaluation and investigation FAPI-PET/CT might have a beneficial role in the management of NETs.