Background: Breast cancer is the most frequently diagnosed life-threatening malignancy among women, across the globe. HER2 positive is a distinct breast cancer subtype, on account of its unique biology and physiological behavior. Results: Amplification of HER2 oncogene/polysomy 17 leads to HER2 overexpression that is a significant causal implication in HER2 positive breast cancer. HER2 gene variants, as well as other genes/gene variants, are involved in its overexpression, disease prognosis and in predicting the susceptibility towards HER2 positive breast cancer. Trastuzumab (Herceptin) is the most commonly used therapy for treating patients with HER2 positive status. Genomic alterations are incriminated in the development of trastuzumab-resistance, which influences the response towards trastuzumab-therapy. Conclusion: In the current review article, we have summarized the genomic alterations that are responsible for overexpression of HER2 and therefore, increased risk of breast cancer. In addition, the gene variants affecting response towards trastuzumab-therapy have also been discussed. ? 2017 Bentham Science Publishers.
