Tumors were then classified as luminal A (ER+, PR−/PR+, HER2−), luminal B (ER+, PR−/PR+, HER2+), HER2 (ER−, PR−, HER2+), and TNBC (triple-negative breast cancer) (ER−, PR−, HER2−) based on receptor status (30). The gene discussed is ESR1; the disease is triple-negative breast carcinoma.