Acute Cholangitis Masquerading Biliary Neuroendocrine Carcinoma: A Rare Twist to a Typical Presentation.

Biliary neuroendocrine carcinoma (BNEC) develops in the biliary tract and is characterized by the presence of neuroendocrine cells and account for less than 1% of all malignancies. We present a patient with no significant risk factors of BNEC who presented with abdominal pain and jaundice. An endoscopic ultrasound with endoscopic retrograde cholangiopancreatography was concerning for neoplasm and less likely Mirizzi syndrome. Pathology revealed well-differentiated grade 3 large-cell neuroendocrine carcinoma of the common bile duct. BNEC has a poor prognosis with a reported 5-year survival rate of less than 20%, which is worse than other biliary tract malignancies such as cholangiocarcinoma. Additional cases and further studies of multimodal treatment are required in the future to improve prognosis. Providers should be aware of the risk factors of BNEC and consider the diagnosis when evaluating patients with the symptoms above.