Breast cancer (BC) is the most common and it has the highest mortality rate among women.1It can be staged according to tumor size, number of lymph nodes, and whether there is distant metastasis.2The tumor can also be positive for estrogen/progesterone receptors, which directs the treatment to an oral hormone therapy (HT) with tamoxifen or aromatase inhibitor (AI). The gene discussed is CYP19A1; the disease is breast cancer.