Assessment of Estrogen Receptor Beta in Patients with Triple Negative Breast Cancer

Introduction: Triple negative breast cancer (TNBC), defined as lacking the expression of estrogen receptor alpha (ERα), progesterone receptor and human epidermal growth factor receptor is an aggressive breast cancer subtype for which there is a need to identify new therapeutic targets. About 50-80% of TNBC express Estrogen Receptor Beta (ERβ). Given its slight differences from ERα in terms of structure, signaling and its anti-proliferative effects on breast cancer cells, ERβ may be a possible therapeutic target. This study sought to assess the presence of ERβ and its correlation with the clinico-pathological features among the Egyptian females with TNBC. Material and Methods: The study was a retrospective analysis. The following data was retrieved from patient’s files and recorded: age, tumor size, lymph nodes metastasis, and stage. Paraffin blocks for patients confirmed by IHC to be TNBC were subjected to immunohistochemical staining for ERβ, CK5/6, and Ki 67. Results: ERβ was positive in 80% of cases (n=32/40). ERβ significantly correlated with Age (rs = -0.473, P = 0.002, n = 40), Tumor size (rs = -0.471, P = 0.007, n = 40), Lymph nodes (rs = -0.365, P = 0.021, n =40), and Stage (rs = -0.468, P = 0.002, n = 40). There was no correlation between ERβ with Ki-67 and CK5/6 a marker of the basal phenotype. All 8 patients without ERβ had an aggressive disease. 4 received neoadjuvant chemotherapy with minimum or no pathologic complete response in the axillary lymph nodes, 2 presented with upfront metastatic disease while the other 2 were cases of local recurrence with a change in the molecular phenotype of the tumor from luminal subtype to TNBC. Conclusion: This study shows ERβ expression occurs in TNBC. It may have the potential to become a therapeutic target for TNBC.