That is, luminal A (ER+/PR+HER2-), luminal B (ER+/PR+HER2+ or ER+/PR+ Ki67 > 14%), HER2 (ER-PR-HER2+), and triple-negative breast cancer (TNBC, ER-PR-HER2-). The gene discussed is ESR1; the disease is triple-negative breast carcinoma.