Comparison of the HER2/neu gene amplification assesment by differential PCR and immunohistochemistry in breast cancer patients in Isfahan

Background and aim: Amplification of the oncogene HER-2/neu influences the breast cancer progression, prognosis and therapy. Accurate assessment of HER-2/neu status of the tumor is important for management of the disease and correct selection of patients who are able to respond to trastuzumab neu treatment. This study designed to evaluate the HER-2/neu gene status in breast cancer specimens by differential PCR and to show the concordance between these evaluations and IHC test in some specimens. Methods: In this case-control study the quantitative accuracy of differential PCR was evaluated and then 67 fresh and 16 formalin fixed paraffin embedded breast cancer tissues were analysed using this method. IHC reports were available only for 27 of these samples. Data were analysed using McNemar and kappa test. Results: HER-2/neu gene amplification was estimated (35%) in 29 cases out of 83 specimens (35%), as shown by differential PCR. IHC reports showed that 12 out of the 27 specimens contain overexpressed HER-2/neu. So, there was 70% agreement between these two methods (19 out off 27). Among the 8 discordant samples, 6 cases were negative by IHC but positive by differential PCR and 2 cases with HER-2/neu amplification had normal HER-2/neu expression by IHC. Conclusion: Differential PCR is a simple, rapid and cheap method to determine the gene dosage in samples with small amount of tumor tissue but it does not seem to be so accurate, as it compares the end point products of the PCR. Thus, this method has low accuracy and the observation of 6 cases with HER-2/neu amplification in the absence of HER-2/neu over expression may have come from this reality