Histologic prognostic factors, which predict the risk of death and recurrence from BC, can be morphological, including tumor histology, tumor nuclear grade, lymphatic and vascular invasion, and molecular, such as estrogen-receptor (ER) and progesterone-receptor (PgR) status, epithelial growth factor receptor HER2 status, and expression of proliferation-related genes, such as Ki-67 [4,5,6,7]. The gene discussed is ESR1; the disease is breast cancer.