Case Presentation: A 27-year-old woman with no significant past medical history presented with three months of sharp abdominal pain, pruritus, and dark urine. Her labs at admission revealed a mixed hepatocellular–cholestatic liver injury. CT demonstrated a hypo-enhancing mass at the hepatic duct confluence measuring 2.5 x 1.5 cm along with intrahepatic biliary dilatation, which was initially concerning for hilar cholangiocarcinoma. ERCP demonstrated high-grade hilar stricture with dilated intrahepatic ducts, which were treated with plastic stenting to the left intrahepatic duct. Stricture biopsies revealed a well-differentiated NET which stained positive for chromogranin, synaptophysin, CK7, and INSM1 with a low proliferative index on initial sampling. Serum chromogranin A, CA 19-9, AFP, and 24-hour urinary 5-HIAA were unremarkable. PET scan demonstrated signal confined to the hilar lesion without evidence of extrahepatic disease, which raised the possibility of a primary perihilar NET but did not exclude occult metastatic primary malignancy. Prior to planned surgical resection, she was readmitted for acute ascending cholangitis due to biliary stent dysfunction, which was successfully treated with stent exchange and biliary decompression. She subsequently underwent extended right hepatectomy with bile duct resection and Roux-en-Y hepaticojejunostomy. Final pathology demonstrated a 2.3 cm well-differentiated NET (WHO grade 2, Ki-67 15%) in the perihilar soft tissue with infiltration into adjacent liver parenchyma. There was extensive perineural and vascular invasion, negative bile duct and vascular margins, and histologically normal background liver. Given complete macroscopic resection, lack of metastatic disease, and well-differentiated histology, no adjuvant therapy was pursued. She is due for surveillance cross-sectional imaging and endoscopic evaluation to exclude an occult primary gastrointestinal source.
Discussion: Neuroendocrine tumors (NET) are exceedingly rare, accounting for 0.5% of malignancies, with primary sites of malignancy including the gastrointestinal tract and the lungs (2). Neuroendocrine tumors that arise along the extrahepatic ducts are often misdiagnosed as perihilar cholangiocarcinoma, with final diagnosis arising only in post-operative pathology (3). The ultimate management of both malignancies differs: Klatskin tumor management involves not only surgery, but also neoadjuvant chemotherapy and radiation, with liver transplantation reserved for unresectable cases, while surgery can be potentially curative for NET (4,5). Early differentiation between the two pathologies is key, especially to avoid delays in care and unnecessary transplant work-up in unresectable cases; however, it is also exceedingly difficult (5). This case highlights the role of endoscopic retrograde pancreatography (ERCP) with advanced tissue biopsy and functional imaging in the early diagnosis of NET.
Conclusions: Perihilar neuroendocrine tumors (NETs) are exceedingly rare, and presentation along with imaging can closely mimic perihilar cholangiocarcinoma (Klatskin tumors). Further, it is notable that this case involved a young healthy adult without underlying liver disease or hereditary cancer. Early identification of these cases can avoid unwarranted liver transplant evaluation.
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