Her2 amplification status in Iranian breast cancer patients: comparison of immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH).

INTRODUCTION: Her2/neu is a biomarker which is amplified and/or overexpressed in a subset of breast cancer patients who are eligible to receive trastuzumab. Her-2 gene amplification analysed by fluorescence in situ hybridisation (FISH) and/or protein over-expression detected by immunohistochemistry (IHC) are the two main methods used to detect Her-2 status in clinical practice. The concordance rate between the two techniques is controversial. METHODS: FISH analysis were performed on 104 tumoural samples from breast cancer patients with known IHC results to determine the Her2 gene status. The FISH/IHC analyses results were then compared and the concordance rate was determined. RESULTS: Her2 gene amplification was detected in 0 of IHC score 1+, 24/86 (27.91%) 2+, and 8/13 (61.54%) 3+. The IHC and FISH results concordance rates were 100%, 27.9%, and 61.5% for IHC scores of 1+, 2+, and 3+ respectively. CONCLUSION: The results of this study suggest that IHC 1+ should be considered as negative while IHC 2+ results need further confirmative analysis by FISH. Further quality control and standardization of IHC technique are required to improve the concordance rate between the two methods.