Comparison of fluorescence in situ hybridization and immunohistochemistry assessment for Her-2 status in breast cancer and its relationship to clinicopathological characteristics

Abstract

To investigate the concordance and correlation between fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) assessment for HER-2 status in breast cancer patients and analyze their relationship to clinical characteristics. A total of 128 samples of breast cancer tissue were analyzed retrospectively. FISH was employed to detect the HER-2 gene amplification. And the FISH findings were compared with IHC test results by analyzing the concordance and correlation between two results. And their relationships to the clinical characteristics were analyzed. The overall coincidence rate of IHC and FISH was 90.6% (kappa = 0.405, P = 0.000). And the discordance was mainly found in the IHC (++) group. A positive correlation was found between the two results (r = 0.655, P = 0.000). The ER (estrogen receptor) expression was negatively correlated with HER-2 gene amplification and the expression of Her-2 protein (r = -0.300, P = 0.001; r = -0.223, P = 0.011). There was a negative correlation between ER/PR status and HER-2 gene amplification (r = -0.213, P = 0.016). The similar results were found in subgroup analysis. Tumor grade was negatively correlated with the expression of Her-2 protein (r = -0.293, P = 0.008), but not with HER-2 gene amplification (P > 0.05). IHC is a preferred method to detect the Her-2 status in breast cancer. The strong positive expression (+++) of HER-2 protein tested by IHC is strongly consistent with HER-2 gene amplification by FISH. But HER-2 gene amplification should be further detected by FISH in patients with HER-2 positive expression (+-++) in order to guide the clinical diagnosis and treatment. ER, ER/PR (progesterone receptor) status and tumor grade are correlated with HER-2 gene amplification and/or the expression of Her-2 protein. This study helps improve the accuracy of judging HER-2 gene amplification according to the clinical and pathological features such as ER status and the results of IHC.