Intraductal papillary neoplasms of the bile duct

Abstract

Intraductal papillary neoplasm of the bile duct (IPNB) is a rare variant of bile duct tumors characterized by papillary growth within the bile duct lumen and is regarded as a biliary counterpart of intraductal papillary mucinous neoplasm of the pancreas. IPNBs display a spectrum of premalignant lesion towards invasive cholangiocarcinoma. The most common radiologic findings for IPNB are bile duct dilatation and intraductal masses. The major treatment of IPNB is surgical resection. Ultrasonography, computed tomography, magnetic resonance image, and cholangiography are usually performed to assess tumor location and extension. Cholangioscopy can confirm the histology and assess the extent of the tumor including superficial spreading along the biliary epithelium. However, pathologic diagnosis by preoperative biopsy cannot always reflect the maximum degree of atypia, because IPNBs are often composed of varying degrees of cytoarchitectural atypia. IPNBs are microscopically classified into four epithelial subtypes, such as pancreatobiliary, intestinal, gastric, and oncocytic types. Most cases of IPNB are IPN with high-grade intraepithelial neoplasia or with an associated invasive carcinoma. The histologic types of invasive lesions are either tubular adenocarcinoma or mucinous carcinoma. Although several authors have investigated molecular genetic changes during the development and progression of IPNB, these are still poorly characterized and controversial.

Figure 1

Representative images of intraductal papillary neoplasm of the bile duct on computed tomography. Localized bile duct dilatation and an intraductal mass are shown (arrows).

Figure 2

A representative case of intraductal papillary neoplasm of the bile duct with mucin hypersecretion. (a) Endoscopic retrograde cholangiogram. Diffuse dilatation of the common bile duct with amorphous filling defect is shown. (b) Duodenoscopy shows a dilated papillary orifice with mucin.

Figure 3

Peroral cholangioscopy reveals a papillary tumor within the lumen of the bile duct, but no obvious superficial spreading along the biliary epithelium is observed.

Figure 4

Macroscopic findings of intraductal papillary neoplasm of the bile duct. (a) A polypoid mass (arrow) is elevated into the lumen of the bile duct. (b) Polypoid mural nodules (arrowheads) are observed in the well-defined cystic lesion. This lesion was communicated with the bile duct.

Figure 5

Microscopic findings of intraductal papillary neoplasm of the bile duct. Prominent papillary proliferation with delicate fibrovascular cores is a characteristic feature. Epithelial subtypes are classified as pancreatobiliary (a), intestinal (b), gastric (c), and oncocytic (d).