An unusual presentation of metastatic colorectal cancer mimicking cholangiocarcinoma

Background: While liver metastases are common in later-stage colorectal cancer (CRC), metastases that develop more than five years after a curative colectomy is extremely rare. Intrabiliary growth type of metastasis (IGM) is rare with a predicted annual incidence of 0.00067% in the United States. Case Presentation: A 67-year-old female was referred to hepatology by her primary care physician for management of elevated liver function tests in the setting of mixed hyperlipidemia. She had a history of Stage 1 CRC 10 years prior, which was treated with a hemicolectomy. Her most recent colonoscopy was performed five months prior. The initial workup included a liver biopsy and antimitochondrial antibody studies, both of which were normal and ruled out primary biliary cholangitis. Subsequent blood work revealed an elevated level of alkaline phosphatase. An MRCP was unremarkable and an MRI showed no biliary duct dilation or evidence of obstruction. In the setting of isolated ALP elevation and a negative workup for any other liver disease, a working diagnosis of an extrahepatic process for elevated ALP was assumed, and the patient was scheduled for follow up in six months. Six months later, the patient was admitted for an unrelated episode of gastritis. Serum studies taken during her admission showed elevated liver function tests. One month after discharge, she was seen in the office for follow-up and was complaining of abdominal pain; her liver enzymes remained elevated. A second MRCP revealed dilation of the right intrahepatic bile ducts which was highly concerning for underlying malignancy. A CEA and CA 19-9 were negative. An urgent endoscopic retrograde cholangiopancreatography (ERCP) with brush cytology was unremarkable and the cytology was negative for malignancy. The patient continued to have abdominal pain and elevated liver function tests, and a second ERCP with cytology was performed. The ERCP revealed a focal stricture in the right hepatic duct. The patient subsequently underwent a balloon dilatation with stent placement. The second brush cytology was positive for malignancy. The patient presented to the emergency department (ED) with complaints of upper abdominal pain and was admitted three days after her second ERCP. An abdominal computed tomography (CT) scan performed in the ED was negative for any obvious liver masses. The patient was discharged a few days later and was referred to surgery for a hepatectomy. A right hepatectomy was performed with no acute complications. On gross exam, the right liver lobe appeared slightly atrophic with no evidence of obvious masses. Histology revealed moderately differentiated adenocarcinoma (8.0 x 1.0 x 1.0 cm) with an intestinal phenotype, most consistent with colorectal adenocarcinoma. The patient underwent a colonoscopy and there was no evidence of recurrent colon cancer; CEA and CA 19-9 levels were within normal limits. Upon follow-up, the patient's ALP levels had improved and her liver enzymes were normalized. Conclusions: This case indicates that a new and unexplained biliary stricture could be a manifestation of metastasis even if no obvious mass is seen.