Younger age at diagnosis (≤ 45 years old) is associated with more aggressive breast cancer biomarkers, including overexpression of ERBB2/HER2 and ERBB1/HER1 growth factor receptors [13], abnormal p53 expression [13,15], estrogen receptor (ER) negativity [12-16], higher nuclear grade and higher Ki-67 proliferation index [12-14,16]. The gene discussed is ESR1; the disease is breast cancer.