Ultrasound-guided core biopsy showed moderately differentiated invasive ductal carcinoma (IDC), estrogen receptor (ER) positive in >90%, progestin receptor (PR) positive in >90%, and human epidermal growth factor receptor 2 (HER2) positive by immunohistochemistry (IHC), but fluorescence in situ hybridization (FISH) was negative. The gene discussed is ERBB2; the disease is invasive ductal breast carcinoma.