Bile duct neoplasms are a heterogeneous group of benign and malignant tumors. This chapter provides an overview of bile duct tumors and precursor lesions. It covers benign biliary lesions such as bile duct adenomas and von Meyenburg complexes, highlighting their differences. The chapter also discusses mucinous cystic neoplasms of the liver, including their grading, and intraductal papillary neoplasms of the bile ducts (IPNB), which are precursors to cholangiocarcinoma. IPNB can occur in various locations, including intrahepatic, hepatic hilum, or extrahepatic bile ducts, with distinct epithelial differentiation patterns. Intrahepatic cholangiocarcinoma (iCCA), an aggressive liver malignancy with rising global incidence, often presents diagnostic challenges. The chapter outlines iCCA’s classification and its subtypes, each with distinct clinicopathologic features, mutational profiles, and prognoses. Lastly, the chapter explores key immunohistochemical markers and panels for diagnosing iCCA and distinguishing it from metastatic carcinoma.