An Unusual Case of Rectal Bleeding due to Metastasis from Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a rare, yet aggressive form of cancer that can originate from the epithelium to anywhere along the bile ducts (BD). Depending on the locations of the CCA, the treatment, prognosis, and diagnosis can be greatly impacted. The primary risk factors are sclerosing cholangitis and choledochal cysts. Anatomically, CCA are classified as intrahepatic (IH) and extrahepatic (EH). EH further divided into distal and perihilar. These subtypes have common features but also important differences that affect the pathogenesis and outcome. Histologically, a great majority of these (90%) are adenocarcinomas with the remainder being mostly squamous cell carcinomas. It is possible to support a diagnosis of malignant biliary epithelium through immunohistochemical staining. Specifically, cytokeratin-7 (CK-7) positivity is consistent with biliary tract origin. The clinical presentation of CCA varies, with some patients presenting with jaundice. However, most cases are silent and are not diagnosed until the advanced stage. Common sites of metastasis include the liver, peritoneum, and brain. Although rare, colon metastasis has been reported and requires a high index of suspicion for early detection. Here, we present a rare case of a patient with intermittent rectal bleeding secondary to colon metastasis from CCA.