ERBB2 and cancer: To address such lack of information, we performed a comprehensive analysis of deep whole-exome sequencing (WES) data from breast cancer patients in the Taiwanese population (BCTW), to infer the impact of WGD, along with frequent cancer gene alterations, on the timing of events driving tumor initiation and tumor maintenance within subtypes of breast cancer (hormone receptor-positive and human epidermal growth factor 2 receptor-negative (HR + /HER2-), HR + /HER2 + , HER2 + , and triple-negative (TNBC)).