Qap (Anatomical Pathology) 

Case: AP324
Contributor's Comment: This diagnosis is best attained by a low-power view of the portal tracts, featuring several cystically dilated bile ducts arranged around traversing fibrovascular tissue ?indicating ductal plate malformation. Actually the gross morphology (see photo) shows the characteristic malformation ?circular ladder-like arrangement of the dilated duct lumen (if the stones are not obstructing the view).

This case is complicated by cholangitis and secondary stone formation, hence leading to an erroneous diagnosis of recurrent pyogenic cholangitis/primary hepatolithiasis by most participants. The ectatic ducts in RPC usually show fusiform dilatation, and the stones are dark brown to black (calcium bilirubinate type). There is more florid peribiliary proliferation. The type of stones present in this case is not typically of those in RPC.

Ref: TsuiWMS, Lam PWY, Lee WK, Chan YK. Adv Anat Pathol 2011;18:318-328