Mixed adenoneuroendocrine carcinoma of the distal bile duct: A case report

INTRODUCTION: Mixed adenoneuroendocrine carcinomas (MANECs) of the distal bile duct are extremely rare, and only a few cases have been reported in the English literature. PRESENTATION OF CASE: An 82-year-old man was referred to our hospital for increasing biliary enzymes. Abdominal computed tomography (CT) showed enlargement of the intrahepatic bile ducts and stenosis of the distal bile duct. Endoscopic retrograde cholangiopancreatography showed stenosis of the distal bile duct and a high-density signal at the same site on diffusion weighted imaging. PET-CT showed increased FDG accumulation (SUVmax: 4.5) at the distal bile duct stenosis. Biopsy specimens obtained by endoscopic ultrasonography-guided fine-needle aspiration revealed adenocarcinoma. The patient was diagnosed with adenocarcinoma of the distal bile duct and underwent subtotal stomach-preserving pancreaticoduodenectomy with regional lymph node dissection. The resected distal bile duct tumor was 18 × 14 × 12 mm in diameter. Hematoxylin and eosin staining revealed a composite carcinoma with adenocarcinoma and non-adenocarcinoma elements. The non-adenocarcinoma component stained positive for synaptophysin and chromogranin A. The Ki-67 labeling index was 37%. The non-adenocarcinoma component was therefore diagnosed as a neuroendocrine carcinoma. The two composite carcinoma was diagnosed as MANEC of the distal bile duct. The patient was treated with surgery alone and he remained disease-free for 7 months after the surgery. DISCUSSION: The treatment of MANECs of the bile duct remains controversial and the prognosis is poor. CONCLUSIONS: There is no standard treatment for MANECs of the bile duct. Larger studies are required to establish standard treatment regimens.