A Case of Long-Term Survival after Multimodal Treatments including Living-Donor Liver Transplantation for a Primary Neuroendocrine Tumor of the Bile Duct.

INTRODUCTION: An extrahepatic biliary neuroendocrine tumor (EB-NET) is an extremely rare malignancy with a poor prognosis and no established standard of care. CASE PRESENTATION: We herein report the case of a 35-year-old Japanese woman with no significant past medical or family history who presented with epigastric and back pain and was diagnosed with an EB-NET after pylorus-preserving pancreaticoduodenectomy. Despite initial resection, she developed recurrent liver metastases that required repeated hepatic resections and multiple systemic therapies, including chemotherapy, somatostatin analogs, everolimus, and peptide receptor radionuclide therapy (PRRT). Eventually, owing to progressive liver metastasis, she underwent living-donor liver transplantation (LDLT) from her brother 6 years after the initial surgery. Post-transplantation, the patient has remained disease-free for >3 years while on maintenance immunosuppression. CONCLUSIONS: Multimodal treatment, including resection of metastases, PRRT, and LDLT, significantly prolonged survival. This case highlights the potential role of LDLT as a curative strategy for patients with EB-NETs and controlled extrahepatic disease following multimodal treatment. Our case suggests that liver transplantation may provide long-term survival even in cases of a rare primary EB-NET, prompting the consideration of broader transplant indications in selected patients.