Comparison of fluorescence in situ hybridization and immunohistochemistry for assessment of HER-2 status in breast cancer patients.

The accurate assessment of a proto-oncogene, human epidermal growth factor receptor-2 gene (HER-2), is extremely important for the therapy and prognosis of breast cancer. Currently, immunohistochemistry (IHC) is the method widely used for the detection of HER-2 protein. Fluorescence in situ hybridization (FISH) has been suggested to be a golden standard assay for HER-2 amplification. This study examined the expression and amplification of HER-2 in paraffin-embedded sections of breast cancer tissues, and compared the two methods on the measurement of HER-2 status. HER-2 gene and protein were determined in breast cancer samples from 52 Chinese women by FISH and IHC respectively. The findings indicated that the HER-2 gene amplification was found in 18 cases (34.6%) by FISH and the HER-2 protein over-expression (score 3+) in 15 cases (28.8%) by IHC. Immunohistochemically, 28.6% of the cases scored as 2+ and 93.3% of the cases scored as 3+ were HER-2-positive by FISH. There was a significant correlation between the HER-2 gene amplification and HER-2 protein over-expression in breast cancer (P<0.005). No correlation was noted between the HER-2 gene amplification and any of the clinicopathological parameters examined, including age, menopausal status, menarche age, tumor size, histological tumor type, histological grade, lymph node status, and the expression of ER and PR. It was concluded that the detection of HER-2 gene amplification in breast cancer by FISH is valuable and can compare with HER-2 protein detection by IHC.