Testing tumor type dependent relations between expression of ER and PgR with Ki-67 values in a single series of 1180 invasive ductal cancer patients

Background: Model of cancer-associated epigenetic changes (Kurbel S. Tumour Biol. 2013;34:2011-7) proposes that dysfunctional estrogen receptors (ER), unable to adequately express progesterone receptors (PgR), beside in the ER+PgR– breast cancers might also be present in ER+PgR+ tumors showing weak PgR expression. Methods: In 1180 patients with invasive ductal cancers, ER and PgR positivity were semiquantitatively classified in four groups: “0” means no positive cells; “1+” <10% positive cells; “2+” 11–30% positive cells; and “3+” 31–100% positive cells. Tumors were divided in breast cancer types. Results: Among patients older than 54, Luminal A and B1 tumors were frequently ER3+ (p20%). The predicted values matched well with the found shares of ER3+PgR1+ tumors within these three types (p>0.10). Conclusions: The results support heterogeneity among ER+PgR+ tumors. Future studies of ER+PgR+ phenotype variants are required since hypothetical dysfunctional ERs in some ER+PgR+ breast cancer patients might alter their endocrine treatment outcomes