Pathologic patterns of invasive carcinoma associated with intraductal papillary neoplasms of bile duct (IPNB)

The pathologic features of invasive carcinoma associated with IPNB remain to be clarified. By using 82 cases of IPNB, the pathologic spectrum of associated invasive carcinoma and its correlation with their post-operative overall survival (OS) were examined. Invasive carcinoma was found in 52 cases (63 %) of IPNB and was classifiable into three patterns (patterns A, B and C). Pattern A was characterized by microscopic foci of invasive carcinoma in the fibrovascular stalks or confined to the bile duct mucosa and wall beneath the intraluminal pre-invasive neoplastic components of IPNB (23 cases) and pattern B by invasive carcinoma in the periductal connective tissue and in the adjacent organ(s) mainly near or beneath the intraluminal component(s) of IPNB (15 cases). Pattern C showed nodular invasive carcinoma considerably involving the intraluminal pre-invasive components and the bile duct mucosa and wall adjacent to the intraluminal pre-invasive components of IPNB (14 cases). Recognition of these three patterns of invasive carcinoma associated with IPNB may expand the pathologic spectrum of IPNB. IPNBs without invasive carcinoma showed a favorable post-operative-OS compared with those with invasion as a whole and those of pattern B and C, respectively, but showed a similar post-operative-OS to that of pattern A. IPNB of pattern B and C showed an unfavorable post-operative outcome, though there was no difference between pattern B and C. Understanding of the pathologic spectrum of associated invasive carcinoma may facilitate further pathological analysis of IPNB.