In contrast to most solid tumors, breast cancer tissues show significantly higher zinc levels compared with normal breast tissue.136,173,174,175,176 Zinc distribution and zinc transporter levels show distinct profiles in breast cancer subtypes.142 Breast cancer is classified into basal (or triple negative), human epidermal growth factor receptor 2 (HER2) overexpression and luminal (or estrogen receptor positive, ER+) A (low-grade) and B (high-grade) tumors. The gene discussed is ESR1; the disease is breast cancer.