The gene cluster was significantly more expressed (P ≤ 0.01) in estrogen receptor and progesterone receptor negative tumors (ER−/PR−), which are classified as the most aggressive and least differentiated breast tumors (16), compared to ER+/PR+ tumors (Figure 4C), as well as in EMT tumors compared to non-EMT tumors (P ≤ 0.01) (Figure 4D). This evidence concerns the gene PGR and breast neoplasm.