Evaluation of HER2 In Breast Cancer Patients of Saudi Arabia using Conventional Immunohistochemistry and Modern Bright-Field Double IN Situ Hybridization

The aim of this study was to evaluate the prevalence of human epidermal growth factor receptor 2 (HER2/neu) gene/protein amplification/expression patterns in breast cancer (BC) of Saudi patients by using conventional immunohistochemistry (IHC) and bright-field double in situ hybridization (BDISH) techniques. King Abdulaziz University Hospital (KAUH), Jeddah, Kingdom of Saudi Arabia. A total of 128 consent patients’ (aged 24 to 81 years) samples of breast cancer were subjected to screening for HER2/neu protein expression by immunohistochemistry (IHC) and later for amplification by bright-field dual in situ hybridization (BDISH) method. The clinicohistopathological data of all the patients were collected from the patients’ case records. The expression of the HER2/neu protein was evaluated, correlated to HER2/neu gene amplification status in BC and assessed for potential clinical value by correlation measures. IHC data determined that HER2/neu protein expressed in 18-20% (3+) of our BC patients in Saudi cohort. Some samples showed moderate membranous expression of HER2/neu protein and majority of samples showed either negative or 1+ expression. 73% of all the invasive ductal breast carcinoma tissue slides showed non-amplification HER2/neu gene status and 27% showed amplification HER2/neu gene status. Interestingly, there was a reasonable concordance rate (77 %) between IHC and BDISH data in the analyzed cohort. In conclusion, HER2/neu expression/amplification status in breast cancer of Saudi patients is within the range as compared to other ethnic groups. This HER2/neu (over-expression/amplification) status was concordant using either IHC or BDISH and significantly associated with disease aggressiveness and poor outcome.