We experienced a case of mass-forming intrahepatic cholangiocarcinoma which could not been diagnosed accurately without pathologic findings. A 78-year-old Japanese woman with no particular symptoms was admitted for changes in liver function tests. Ultrasonography revealed a solid liver tumor. When there are no typical imaging features, no pathognomonic clinical findings and no obvious risk factors for any specific hepatic tumor, it may be difficult to make an accurate diagnosis before surgical resection. The lesion was resected on the basis of a high degree of suspicion for malignancy and submitted for pathologic evaluation. Microscopically, the neoplasm was a moderately differentiated adenocarcinoma with abundant fibrous stroma, consistent with a mass-forming cholangiocarcinoma. This case exemplifies the importance of considering the various tumorous and non-tumorous diseases in the differential diagnosis of a liver mass with atypical features, especially when malignancy cannot be excluded.
Keywords: Mass-forming intrahepatic cholangiocarcinoma; Moderately differentiated adenocarcinoma.