In addition to traditional pathological characterization and immunohistochemistry (IHC) to examine protein levels of markers such as estrogen receptor (ER), progesterone receptor (PR), and epidermal growth factor receptor-2 (HER2), additional studies evaluating genomic rearrangements and molecular expression profiles of breast cancers have provided further genetic insights to better understand the disease4–6. Here, ESR1 is linked to breast carcinoma.