Chiefly, the cells lining the milk-forming duct of the mammary glands are the origination of breast cancer (Herbein and Kumar, 2014) which can be further subdivided based on the presence or absence of the hormone receptors i.e., estrogen and progesterone subtypes and human epidermal growth factor receptor-2 (HER2). The gene discussed is NR4A1; the disease is breast cancer.