Intrahepatic cholangiocarcinoma with predominant ductal plate malformation pattern

Cholangiocarcinoma arising in the liver can be classified into intrahepatic (or peripheral) cholangiocarcinoma (ICC) or perihilar cholangiocarcinoma, depending on the topographic location of the tumor along the intrahepatic biliary tree. Grossly, peripheral ICC usually presents as a mass-forming type, while perihilar ICC may present as mass-forming, periductal infiltrating, or intraductal-growth types. Histologically, ICC is heterogeneous: while the majority of ICC present predominantly as a mucin-producing adenocarcinoma, some tumors take the form of a cholangiolocellular carcinoma (CCC), and others demonstrate mixtures of these components within the tumor. Recently, Nakanuma et al proposed a new subtype of ICCs resembling the histologic features of ductal plate malformation (DPM). DPM is a developmental anomaly in which the fetal ductal plate persists after birth, and is found mainly in congenital or various acquired hepatobiliary diseases. ICC with DPM pattern is histologically characterized by irregular and tortuous glandular structures with bridge formation, biliary cell projections into the lumens, and intraluminal tumor cells. The histopathologic findings of ICC with predominant DPM pattern are discussed, based on the following case which we recently encountered. CASE