Determination of HER2 Gene Amplification using Chromogenic in Situ Hybridization (CISH) in Iraqi Patients with Breast Carcinoma

Background: Breast cancer is the most common malignancy among women worldwide.The human epidermal growth factor receptor (HER) is a transmembrane receptor in the epidermal growth factor (EGF) receptor family located at the long arm of human chromosome 17 (17q12). Diagnostic assays for HER2 in breast cancer provide important prognostic information and independently help guide management by identifying patients who are the most likely to benefit from Herceptin-targeted therapy. Objective: To evaluate the Efficiency of using CISH technique in Equivocal Immunohistochemical results of HER2 protein. Materials and Methods: Sixty cases of breast cancer were subjected to immunohistochemistry for expression of HER2 protein.The genetic status of HER2 gene were determined using Chromogenic In Situ Hybridization (CISH) to discriminate the equivocal results of score 2 immunohistochemical expression. Results: within the Equivocal cases, 24.5 % (12 out of 49) showed low amplification results while 8.1%(4 out of 49)showed high amplification results the rest showed no amplification result. Conclusion: Integration of CISH in Iraqi diagnostic laboratories during HER2 testing algorithm of all equivocal HER2 IHC(2+) test result provides a convenient definitive guidance for accurate HER2 gene amplification status to discriminate these results.