Tumours of the biliary system

Biliary hamartoma, bile-duct adenoma (BDA) and mucinous cystadenoma are the most common benign biliary tumours. Hamartomas occur sporadically or in association with polycystic liver disease. BDAs may represent a localized response to injury rather than true neoplasms. Cystadenomas are multilocular lesions lined by mucinous epithelium, often with cellular ovarian-like stroma. Cytologic atypia may suggest malignant transformation, but stromal invasion must be identified for diagnosis of cystadenocarcinoma. Cholangiocarcinoma (CC) is the most common malignant neoplasm. Risk factors include primary sclerosing cholangitis, liver flukes, hepatolithiasis and thorotrast exposure. The tumours show mass-forming, periductal-infiltrating or intraductal growth patterns. Intrahepatic CC presents as a hepatic mass and can be confused with hepatocellular carcinoma or metastatic adenocarcinoma. Immunohistochemistry and albumin in situ hybridization are helpful in this distinction. The diagnosis of extrahepatic CC can often be elusive due to the marked stromal desmoplasia, and multiple endoscopic biopsies and brushings may be required. Loss of p53 is common in mass-forming intrahepatic CC, and K-ras mutations in periductal-infiltrative extrahepatic tumours. Prognosis is poor, with 5-year survival of <20%. Lymph-node metastasis and surgical margin status are the most significant prognostic factors.