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 Χ(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.
Keywords: Breast cancer; HER2; clinical pathological features; fluorescence in situ hybridization (FISH); immunohistochemistry (IHC).