Background : Intrahepatic Cholangiocarcinoma (iCCA) is a primary tumor that originates from the progenitor cells of the epithelial cells of the hepatic bile duct. It typically spreads to the lymphatic system, liver, lungs, peritoneum, bones, and adrenal glands. Metastasis to the colon is extremely rare.

Methods : A 66-year-old female, with history of cured ovarian cancer, presented with abdominal bloating, distention, and constipation lasting for 4 weeks. Serologic testing revealed a significant elevation in CA 19-9, measuring 90.4 U/mL. Computed tomography indicated an ill-defined hypodense lesion in the lateral segment of the left lobe of the liver, along with a thickened wall of the cecum. A colonoscopy was conducted, during which a cecal ulcer with edematous mucosa was identified, and biopsies indicated normal tissue. She underwent a left hepatectomy and right hemicolectomy after intra-operative evaluation indicated a cecal mass.

Results : The patient underwent a left hepatectomy along with colon tumor resection and lymph node dissection, initially diagnosed as primary colon cancer. However, histological examination of the liver and colon indicated metastatic pancreaticobiliary type adenocarcinoma, which invaded the serosa from the primary intrahepatic cholangiocarcinoma. The findings revealed moderately differentiated adenocarcinoma with neural invasion, but no lymph node metastasis was observed.

Conclusions : While exceedingly uncommon, CCA with colonic metastasis can mimic simultaneous primary colon cancer and cholangiocarcinoma, as well as colon cancer with liver metastasis. Preoperative investigation can inform the operative planning. Final immunohistological staining and pathological features are essential for differentiating metastatic from primary cancer, which can significantly impact prognostication and treatment decisions.