Long-term survival after chemotherapy combined immunotherapy for recurrent mixed neuroendocrine-non-neuroendocrine neoplasms of the common bile duct.

Mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) of the common bile duct (CBD) are extremely rare, with few literature reported. A 68-year-old male was admitted to our hospital with choledocholithiasis with acute cholangitis. Abdominal computed tomography showed that the CBD was occupied and clearly dilated. Consequently, the patient underwent pancreaticoduodenectomy with regional lymph node dissection. The resected tumor at the distal bile duct was 25 × 25 × 13 mm, consisting of 30% adenocarcinoma and 70% neuroendocrine carcinoma microscopically. The patient then received six cycles of adjuvant chemotherapy. Subsequently, regular monitoring of the patient's tumor marker CA19-9 showed progressive elevation. The patient was readmitted to hospital for tumor recurrence and metastasis and received palliative second-line Gemcitabine and cisplatin chemotherapy and three courses of combined immunochemotherapy (Tyvyt [Sintilimab] + Gemcitabine + Cisplatin). Throughout the treatment course, the tumor marker CA19-9 persistently remained elevated. The patient achieved an overall survival (OS) of 29 months. We found that the continuous elevation of the tumor marker CA19-9 during follow-up might suggest tumor recurrence and an unfavorable prognosis. For patients with multiple metastases of cholangiocarcinoma, combined immunotherapy could potentially assist in prolonging survival. Currently, there is no standardized treatment for biliary MiNENs, and larger scale studies are needed to establish diagnosis and treatment protocols to improve the overall survival of patients.