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. This evidence concerns the gene PGR and breast cancer.