HER-2 status and its clinicopathologic significance in breast cancer in patients from southwest China: re-evaluation of correlation between results from FISH and IHC

This study aimed to re-evaluate the concordance between FISH and IHC for HER-2 status, and evaluate its clinicopathologic significance in breast cancer by the new guideline (2014) in China. We determined the HER-2 status in 589 cases of invasive breast cancer, the concordance and correlation between these two results and their relationship to cliniopathological characteristics were evaluated. The rate of HER-2 gene amplification identified by FISH was 31.07% (183/589). Concordance was detected in 93.67% with IHC 0/+, 32.26% in IHC 2+, and 61.16% in IHC 3+. The concordance of 54.67% was observed with a Kappa coefficient of 0.189 (P = 0.000), and a positive correlation was found between IHC and FISH (r = 0.427, P = 0.000). Moreover, the expression of ER was negatively correlated with HER-2 gene amplification and the expression of Her-2/neu protein (r = -0.419, P < 0.001; r = -0.144, P < 0.001; respectively), and the PR expression and ER/PR status was negatively correlated with HER-2 gene amplification (r = -0.226, P < 0.001; r = -0.258, P < 0.001), but not significantly with Her-2/neu expression. Interestingly, the tumor size and histological grade were positive correlation with HER-2/neu protein expression. The coincidently positive rate between FISH and IHC in breast cancer is very high, IHC score 0/+ is strongly consistent with HER-2 gene amplification, IHC score 2+~3+ is a preferred method to detect the HER-2 gene status, FISH still remains a standard method of evaluation of the HER-2 gene amplification.