A case of mucinous cholangiocarcinoma is reported. The patient was a 49 year old woman with the complaint of lumbago. Imaging examination disclosed a tumor 3.5 cm in diameter in the right hepatic lobe, which showed low density on computerized tomography scans and low signal intensity on T1–weighted magnetic resonance imaging (MRI) and high intensity on T2–weighted MRI. The hepatic tumor expanded rapidly and multiple pulmonary metastases and peritoneal dissemination developed. The patient died due to respiratory failure 5 months after the initial symptom. An autopsy, a massive tumor (9.5 cm in diameter) containing abundant mucus with several surrounding daughter nodules was found in the right hepatic lobe. Metastases were widespread. Histologically, the tumor was composed mainly of numerous lobulated mucus lakes in which ade-nocarcinoma cells floated. Admixed signet ring cells were also noted. These gross and histologic features differ from those in other mucin-producing hepatic tumors such as biliary papillomatosis and mucinous cystoadenocarcinoma. lmmunohistochemically, the adenocarcinoma cells were strongly positive for carcinoembryonic antigen, Lewis Y, Tn, and T antigens, and moderately positive for carbohydrate antigen 19–9, Lewis X, sialyl-Lewis X and sialyl-Tn antigen. Mature MUCl mucin and core protein of MUCl mucin were also expressed to varying degrees. The rapidly expanding, widespread metastases and poor prognosis found in the present case may be the clinicopathological features of mucinous cholangiocarcinoma.