A colonic metastasis from extrahepatic cholangiocarcinoma after removal of primary tumor: a case report and literature review.

Metastatic cholangiocarcinoma (CCA) to the gastrointestinal tracts has rarely been described in the literature. We report a 54-year-old male patient with radical resection of an extrahepatic CCA who underwent uncommon metastatic pattern. After a recurrence-free period of 2 years, an elevated CA19- 9 initiated a CT scan, showing a tumor at the junction of rectum and sigmoid with enlarged lymph nodes around colon, mimicking a primary colon cancer. Histological diagnosis was adenocarcinoma, and the patient was treated with surgery as a primary colon cancer, but post-operative immunohistochemistry revealed the same pattern as the CCA. As colon is not the common organ for distant spread that makes some challenge to distinguish the colonic metastatic CCA between primary colon carcinoma. Biomarkers (CA 19-9), immunohistological and pathological features play an important role in distinguishing CCA from primary colon cancer. This case taught us a lesson how cancers can spread to unusual sites and mimic other tumor types, that may change the treatment and prognostication significantly.