Primary neuroendocrine tumour of the extrahepatic biliary duct.

Neuroendocrine tumours of the extrahepatic bile ducts are extremely rare, accounting for only 0.2-2% of gastrointestinal tract neuroendocrine neoplasms. Here, we present an incidental finding of this rare tumour, identified during staging scans post-resection of a malignant rectosigmoid polyp and treated with resection and biliary reconstruction. A suspicious, arterially enhancing porta hepatis lymph node was identified on CT and further investigated with liver MRI and 68Ga DOTATATE PET. These revealed a lobulated lesion of the hilum which showed marked avidity without metastases. The patient underwent a successful radical resection of the extrahepatic biliary ducts (including the left, right and common hepatic ducts), the common bile duct and hepaticojejunostomy formation. Histology revealed a 20-mm well-differentiated NET, WHO Grade 2. Two years later, the patient is alive and well without recurrence. This fascinating case illustrates the importance of thorough preoperative planning of surgical resection for tumours at an unusual primary site.