In a South African sample, most breast cancers were hormone receptor-positive, 54% were ER-positive and/or PR-positive, and HER2-negative tumors; 15% were ER-positive and/or PR-positive, and HER2-positive tumors; 11% were ER-negative, PR-negative, and HER2-positive tumors; and 20% were triple-negative tumors.21 Similarly, among our patients, 60% of breast cancers were ER-positive and/or PR-positive, and HER2-negative tumors; 12.5% were ER-positive/HER2-positive tumors; 7.5% ER-negative/HER2-positive tumors; and 20% were triple negative. This evidence concerns the gene ESR1 and breast cancer.