Evaluation of HER2 oncogene amplification and overexpression in breast cancer and their clinical significance

Objective To evaluate the difference and coincidence between the overexpression of HER2 protein by immunohistochemistry(IHC) and HER2 oncogene amplification by fluorescence in situ hybridization(FISH) in breast cancer,and to compare their clinical significance.Methods The overexpression of HER2 protein and HER2 gene amplification on paraffin embedded specimens from breast cancer patients were detected by IHC and FISH,respectively.Results Among 100 breast cancer specimens,25 showed HER2 protein overexpression(+++),and 23 were found to have HER2 gene amplification;there were 12 cases with positive IHC score(++) were detected to have HER2 gene amplification in 2 cases;and 120 cases with HER2 protein expression(+) were detected to have HER2 gene amplification in 1 case;53 cases with HER2 protein expression(-) were detected to have HER2 gene amplification in 2 cases.The correlation between FISH and IHC was 85%(χ2=42.5,P0.0001).Conclusions IHC could be used as a means for initial screening of HER2 status;and a positive IHC score of(+++) could be presumed to indicate breast cancer with HER2 amplification status.