The primary tumor was an invasive ductal carcinoma classified as pT1N1M0 with hormone receptor positivity (estrogen receptor ++, progesterone receptor +++, human epidermal growth factor receptor-type2 (HER2) +) and was treated with surgery, adjuvant chemotherapy, radiation therapy and endocrine therapy (tamoxifen). The gene discussed is ESR1; the disease is invasive ductal breast carcinoma.