A Rare Presentation of Extrahepatic Biliary Neuroendocrine Tumor Diagnosed using 68Ga-DOTA-TOC Imaging, But Undetectable on 68Ga-FAPI Imaging.

Neuroendocrine tumors (NETs) are commonly seen in the small intestine and rarely found within the bile ducts. This low incidence is due to a smaller number of Kulchitsky cells in the extrahepatic biliary tree, which predisposes to the disease. The diagnosis of biliary tree carcinoid preoperatively is very rare, with most cases in the literature being incidentally diagnosed during surgery or being identified on the histopathology report postoperatively. Here, we present an interesting case of an extrahepatic biliary NET which was diagnosed preoperatively.