This is in contrast with ER/PR positive breast cancers, where luminal progenitors were observed to proportionally decrease (Fig. 4e) whilst the number of mature luminal cells showed a marked increase (Fig. 4f)—consistent with the view that mature luminal cells are the cells of origin for ER/PR positive breast cancers—whilst basal cell proportions remained unchanged (Fig. 4g). This evidence concerns the gene PGR and breast cancer.