Proliferating ductules are a diagnostic discriminator for intrahepatic cholangiocarcinoma in FNA biopsies

The histologic distinction of cholangiocarcinoma (CC) from metastatic carci noma and hepatocellular carcinoma (HCC) is difficult. In particular, the di stinction of CC from metastatic carcinoma on morphologic features alone is not possible and is dependent on the identification of an extrahepatic prim ary carcinoma. The proliferative response to many types of liver injury is characterized by a proliferation of either hepatocyte ductular clusters (HD C) or biliary ductular clusters (BDC). This study examined the presence of such ductular reactions in fine needle aspiration biopsies of 20 consecutiv e cases each of CC and HCC, and compared the findings to those of 20 cases of hepatic metastases from a wide variety of sites. All 18 cases of CC with adequate smears showed ductular proliferation of either HDC or BDC type, t he latter being more common; in 13 cases, there were more than 10 ductular clusters per smear. In contrast, only one case of metastatic carcinoma disp layed so many, ductular clusters, this being a case with multiple hepatic d eposits. Five cases of HCC showed more than 10 clusters. The presence of mo re than 10 ductular clusters associated with malignant cells is a useful di scriminator to separate CC from metastatic carcinoma. Diagn. Cytopathol, 20 00;22:359-363. (C) 2000 Wiley-Liss, Inc.