HER2 mutation status in Japanese HER2-positive breast cancer patients

Background Human epidermal growth factor receptor 2 (HER2) gene amplification/overexpression is a major therapeutic target in breast cancer, and has been introduced as a predictive biomarker to identify patients who may benefit from therapy with anti-HER2 agents. HER2 somatic mutations have been reported, and these may influence the effect of HER2-targeted drugs.