Endobiliary metastasis from rectal cancer mimicking intrahepatic cholangiocarcinoma: a case report and review of literature.

PURPOSE: The purpose of this study is to report an unusual case of liver metastasis from carcinoma rectum, which mimicked an intrahepatic cholangiocarcinoma (ICC) radiologically and pathologically, and to review the relevant literature.

PATIENT: A 64-year-old gentleman was treated for carcinoma rectum in our institution with neoadjuvant chemoradiation followed by low anterior resection and adjuvant chemotherapy. Two years later, he was found to have a nodule in the left hepatic duct on imaging. He underwent left hepatectomy.

FINDINGS: The specimen revealed a tumor in the left hepatic duct, microscopically resembling an ICC. However, immunohistochemistry (IHC) showed the tumor cells to stain positively for cytokeratin 20, but not for cytokeratin 7, thus confirming the metastatic nature of the lesion.

CONCLUSION: Endobiliary metastasis from colorectal cancer can mimic ICC, and IHC studies may be needed to differentiate the two. Identifying endobiliary metastasis can have therapeutic and prognostic implications.