Which, further characterized as luminal A (ER+, PR+, HER2-), luminal B (ER+, PR+, HER2+), HER2-enriched, basal-like, and normal-like based on progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER2) status.17 The MCF-7 and T-47D cell line together with other breast cancer cell type MDA-MB-231, have been studied in above two-third of the total publications in Medline.18 The gene discussed is ESR1; the disease is breast cancer.