Evaluation of Her-2/neu in Breast Cancer: Comparison of Immunohistochemistry and Polymerase Chain Reaction

Abstract

Purpose: In breast cancer, Her-2/neu amplification/ overexpression predicts a poor clinical outcome, and enhanced survival benefits have been reported with Her-2/neu targeted therapy. Currently, there are several methods for assessing the amplification/overexpression of Her-2/neu, each having advantages and disadvantages. The aim of this work was to establish a reproducible, sensitive and specific method of testing for Her-2/neu, which could be used in diagnostic pathology laboratories. Materials and Methods: We compared the immunohistochemistry (IHC) detection of Her-2/neu overexpression, with differential polymerase chain reaction (PCR) to assess the gene am plification of the Her-2/ neu, in 163 cases of invasive ductal carcinoma of the breast using paraffin-embedded tissue. In addition, assessment of the appropriate cut off points was established. Results: The overexpression of the Her-2/neu was detected in 39 (23.9%) cases, and its am plification in 37 (22.7%) cases. The methods were positive in 21.5% of cases and negative in 74.8%. There was a 96.3% concordance between the two methods. The sensitivity and specificity of IHC, compared w ith PCR, were 94.6 and 96.8%, respectively. Conclusion: We conclude that the automation of PCR-based Her-2/neu testing approaches is expected to play an increasing role in the future of Her-2/neu testing. Also, we have demonstrated that IHC is a sensitive and specific method for assessing Her-2/neu stati in breast cancer, compared to PCR. The current study indicates that moderate, or strong, complete membrane staining in ≥10% of tumor cells provides an appropriate cut off point compared with PCR. (Cancer Res Treat. 2003;35:96-101)