An important, but not well understood exception is the triple-negative molecular subtype, which is ER and PR-negative and does not express epidermal growth factor-2 (HER-2) receptors; these aggressively metastatic tumors occur predominantly in premenopausal women and constitute approximately 10%–15% of breast cancers in white, but a higher prevalence in black, women. The gene discussed is ESR1; the disease is breast carcinoma.