PGR and breast cancer: In this work, we assumed that to better understand the nature of the black-to-white crossover, as well as to perform a robust separation of the breast cancer population on fractions with distinct breast cancer phenotypes, there is a need to stratify breast cancer subtypes by biological markers, such as estrogen receptor (ER) status and progesterone receptor (PR) status, which have been shown to be associated with breast cancer development [38]–[40].