Gastric subtype of intraductal papillary neoplasm of the bile duct: The pathologic spectrum

Abstract

Background and aims: Intraductal papillary neoplasms of bile duct (IPNBs) remain a challenging entity to manage.

Methods: The pathologic spectrum of 34 gastric subtype of IPNB (gIPNB) cases was examined in consideration of the type 1 and 2 subclassification proposed by Japan-Korea consensus and compared with gastric subtype of pancreatic intraductal papillary mucinous neoplasm (gIPMN) (44 cases).

Results: Type 1 gIPNBs (17 cases) showed regular papillary foveola with variable tubular pyloric glands. Eight of the type 1 gIPNBs showed low-grade dysplasia. Type 2 cases (n = 17) showed complicated papillary and tubular structures and high-grade dysplastic foveola and pyloric glands. Foveolas were predominant in 15 cases, while pyloric glands were predominant in 10 cases, and considerable areas of foveolas and pyloric glands in the remaining: these three were found similarly in type 1 and 2 gIPNB. gIPMNs showed central foveola with a peripheral pyloric gland. Such a pattern was recognizable in type 1 but vague in type 2. Type 1 was frequently found in the intrahepatic bile ducts and showed abundant mucin, as in gIPMNs, while type 2 also occurred in the extrahepatic bile ducts and were pathologically more malignant.

Conclusion: Type 1 lesions shared features of gIPMN, while type 2 lesions differed from gIPMN and were more pathologically malignant.