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 cancerpatients who are eligible to receive trastuzumab. Her-2 gene amplification analysed by fluorescence in situhybridisation (FISH) and/or protein over-expression detected by immunohistochemistry (IHC) are the two mainmethods used to detect Her-2 status in clinical practice. The concordance rate between the two techniques iscontroversial.
Methods: FISH analysis were performed on 104 tumoural samples from breast cancer patientswith known IHC results to determine the Her2 gene status. The FISH/IHC analyses results were then comparedand 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 IHC1+ should be considered as negative while IHC 2+ results need further confirmative analysis by FISH. Furtherquality control and standardization of IHC technique are required to improve the concordance rate betweenthe two methods.