These subtypes include: Luminal A (ER+ and/or PR+, HER2-), Luminal B (ER+ and/or PR+, HER2+), HER2 positive (ER−, PR−, and HER2+), and triple-negative breast cancer (ER−, PR−, and HER2-). The gene discussed is ESR1; the disease is triple-negative breast carcinoma.