Comparasion of two different detection methods for HER-2 protein expression and gene amplification in breast cancer tissue

Objective To compare HER-2 state in breast cancer tissue deteced by fluorescent in situ hybridization (FISH) and immunohistochemistry (IHC) and analyze their correlation. Methods HER-2/neu protein expression and gene amplification were detected by FISH and IHC in 56 newly-diagnosed cases of female breast cancer from July 2008 to July 2009. Results Of the 56 patients, HER-2 protein expression (-), (+), (++), (+++) was 9 cases (16.1%), 29 cases (51.8%), 11 cases (19.6%) and 7cases (12.5%) respectively; 26 cases (46.4%) had HER-2 gene amplification while 30 cases (53.6%) didnt have. Type of HER-2 gene amplification was mainly HER-2(++) and HER-2(+++), and according gene amplification rate was 72 7% and 100%. HER-2 (+) gene amplification rate was 37.9 %(11cases) and no gene amplification was found in HER-2(-) tissue. The HER-2 positive rate using two methods had significant difference(χ2=19.778,P<0.01). HER-2(-) and HER-2(+++) had good consistency with the FISH results(Kappa=0.969),but HER-2(+) and HER-2(+ +) were poorly consistent with the FISH results(Kappa=0.271). Conclusions IHC is the preliminary screening method for detection of HER-2 expression. HER-2(-) and HER-2(+++) have good consistency with the gene amplification, and can guide clinical treatment. Some patients with HER-2(+) and HER-2(++) have HER-2 gene amplification. FISH is needed for targeted therapy. Key words: Breast cancer;  HER-2/neu gene;  Immuno-histochemistry;  Fluorescent in situ hybridization