Outcomes of surgery for 2010 WHO classification-based intraductal papillary neoplasm of the bile duct: Case–control study of a single Japanese institution's experience with special attention to mucin expression patterns

The World Health Organization (WHO) proposed an integrated classification for intraductal papillary neoplasm of the bile duct (IPNB) in 2010. However, IPNB reportedly shows considerable geographic variation. This Japanese single-institution study examined outcomes of surgery for IPNB and the prognostic impact of immunohistochemical mucin expression patterns. Patients with IPNB were identified from 413 patients who underwent curative-intent surgery for biliary tract (excluding gallbladder) neoplasms from 1992 to 2016 by retrospective macro- and microscopic reevaluation of resected specimens. Their clinicopathological variables were analyzed. Twenty-two (5%) 2010 WHO classification-based patients with IPNB were identified. The other 391 patients had common-type cholangiocarcinoma. The histopathological grade was low/intermediate in 2 patients (9%), high in 8 (36%), and invasive carcinoma (ICa) in 12 (55%). The 10-year overall survival rate was 100% in 10 patients with low–high grade IPNB and 69% in 12 patients with ICa. These rates were significantly (p = 0.018) or marginally (p = 0.089) better than that (38%) of 391 other-cholangiocarcinoma patients. In the 12 patients with ICa, R0 or R1 resection, MUC5AC, and MUC6 expression significantly affected survival. Notably, all seven patients with ICa exhibiting MUC5AC expression survived throughout the study period, while four of five patients with ICa who did not exhibit MUC5AC expression died of recurrence (with vs. without MUC5AC: 10-year overall survival, 100% vs. 60%, respectively; p = 0.018). Our 24-year, single institution's experience suggests that Japanese patients with IPNB favorably respond to surgery, even with ICa. MUC5AC and MUC6 expression may be predictive of favorable outcomes.