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.