Histologic differentiation of hepatocellular carcinoma from adenocarcinoma by a simple panel: evaluation of the pitfalls.

The histological differentiation of Hepatocellular carcinoma (HCC) from cholangiocarcinoma (CC) and metastatic adenocarcinoma (MA) of the liver is difficult in some cases and immunohistochemistry (IHC) is necessary for the diagnosis. HepPar-1 is a recently available antibody which seems to be very specific and sensitive for the diagnosis of HCC. MOC31 is an antibody directed against a cell surface glycoprotein and has been shown to be helpful in distinguishing between HCC and CC or MA as a negative marker in HCC. In this study we tried to apply these two markers for the diagnosis of HCC cases as a simple, useful and reliable panel. We selected 101 liver tumors which had proven diagnosis by several antibodies and cilinicopathologic correlation. The tumors with confirmed histologic diagnosis including 35 HCC, 58 MA, 7 CC and 1 combined HCC-CC.. HepPar-1 was positive in 30 of 35 cases of HCC; none of the other tumors were reactive for HepPar1 except for a case of metastatic gall bladder adenocarcinoma which showed areas of hepatoid differentiation in the H&E slides. MOC31 was positive in 5 of the HCC cases and stained 60 of 65 cases of MA. There were 4 cases of HCC with clear cell morphology, in most of which, IHC pattern was not diagnostic and further investigation was needed. As a conclusion the combination of positive Hepar1 and negative MOC31 is highly suggestive for HCC except for the clear cell variant. These two reliable markers are recommended for the initial step of differential diagnosis between HCC and MA and for the confirmation of the histologic diagnosis.