To that end RNA-sequencing data from the TCGA BRCA cohort was obtained and the analysis was focused on invasive ductal carcinomas with reliable data (493 ER+/HER2−, 157 ER− HER2−, 97 HER2+), as well as 112 normal breast samples (NBS) as described in materials and methods. The gene discussed is ESR1; the disease is invasive ductal breast carcinoma.