Human epidermal growth factor receptor 2 expression in breast cancer: correlation with clinical pathological features

The overexpressed HER2 (human epidermal growth factor receptor 2) is a valuable therapeutic target. Precise assessment of HER2 status is thus crucial in the treatment of breast cancer. In this study, formalin-fixed, paraffin-embedded samples of tumors from 304 breast cancer patients who underwent curative surgery procedures between 2011 and 2014 were tested by immunohistochemistry (IHC) as a primary estimate of HER2 status, followed by fluorescence in situ hybridization (FISH). Concordance rate between IHC and FISH was evaluated. The X-2 test was used to evaluate the correlation between HER2 gene amplification status and different clinical pathological features including: (estrogen receptor) ER and (progesterone receptor) PR expression, age, menopausal status and tumor size. The results show that 84.8% of IHC score 3+ cases and 6.2% of IHC score 0/1+ cases were amplified by FISH. After exclusion of group IHC 2+, the concordance rate between FISH and IHC was 87.4%. There was a significant inverse association between expression of hormone receptors (ER and PR) and HER2 amplification (P < 0.001) among the patients studied. However, no relationship was observed between HER2 amplification and age, menopausal status and tumor size (P > 0.05). The data demonstrate a relatively high level of concordance rate for HER2 testing between FISH and IHC, and HER2 overexpression was associated with the levels of ER and PR.