The patient had presented bilateral breast cancer: the left breast cancer was hormone receptor negative, human epidermal growth factor receptor-2 (HER2) positive, and classified as T4bN1M0, stage IIIb, while the right was hormone receptor positive, HER2-negative, and classified as T4bN0M0, stage IIIb. The gene discussed is ERBB2; the disease is breast carcinoma.