[A case of sarcomatoid intrahepatic cholangiocarcinoma that was difficult to diagnose].

A 70-year-old man presented to our hospital with fever and abdominal pain. A mass was found in the left lobe of his liver. Three months later, disseminated peritoneal nodules and ascites appeared. Liver biopsy and review laparoscopy did not lead to a diagnosis. Approximately five months later, a pathological autopsy was performed, and a final diagnosis of sarcomatoid intrahepatic cholangiocarcinoma was made. Differentiating sarcomatoid cholangiocarcinoma from sarcomatoid malignant peritoneal mesothelioma was difficult due to the similarity of clinical and pathological findings. Because the two diseases are treated differently, being able to differentiate them is a challenge in the future.