Intraductal papillary neoplasms of intrahepatic bile duct: a clinicopathologic study of 25 cases

Abstract

To study the clinicopathologic and immunohistochemical features of intraductal papillary neoplasms of the bile duct (IPNB) of the intrahepatic bile duct. The clinical findings, morphologic features and immunophenotype of 25 cases of IPNB were investigated. Of the 25 cases of IPNB, 18 were in the left lobe, 6 were in the hilar bile duct, and 1 was in the right lobe. The average age was 60.6 (26-73) years. The presenting symptom was abdominal pain in 15 cases. Imaging results were variable, including multilobular cysts, mass lesions within the dilated ducts, cholangiolithiasis with dilated bile duct, and solid mass. Gross examinations were concordant with imaging findings. Microscopically, all the IPNB could be divided into four papillary patterns, including 12 gastric type, 8 intestinal type, 4 pancreatobiliary type and 1 oncocytic type. Five IPNB showed mild to moderate atypia, 10 showed high-grade atypia and 10 IPNB were associated with carcinomas.The invasive IPNB were mainly bile duct adenocarcinomas(9 cases), and rarely colloid carcinoma (1 case). Immunohistochemically, IPNB expressed MUC5AC (96.0%, 24/25), MUC2 (32.0%, 8/25), MUC6 (40.0%, 10/25) and MUC1 (12.0%, 3/25). The different MUC expression was commonly associated with specific histological subtype. IPNBs are rare cystic and premalignant neoplasms of the liver. The imaging features vary, but show a common feature of dilated bile duct. The pathologic types and classifications are similar to intraductal papillary mucinous neoplasm of the pancreas. The MUC stains are helpful in diagnosis and histological subtyping.