ERBB2 and hepatocellular carcinoma: Therefore, to determine the association between TOP2A/HER2 amplification and TOP2A/HER2 overexpression in HCC, we investigated gene copy number of both HER2 and TOP2A by fluorescence in situ hybridization (FISH) and protein expressions of HER2, TOP2A, as well as Ki-67, and tumor protein p53 (TP53) by immunohistochemical staining (IHC).