Steroid hormone status and HER2/neu expression in pregnancy-associated breast cancer

Abstract

21115 Background: Breast cancer occurring during pregnancy or within the first year after delivery is considered to be a pregnancy-associated breast cancer. Some studies have shown a decreased estrogen receptor-positive and progesterone receptor-positive status in pregnant patients with breast cancer, others, however, have not. Moreover, little information is available about the expression of HER2/neu and about the other human estrogen receptor, estrogen receptor beta (ERbeta) in pregnancy-associated breast cancers. The aim of this work was to determine the extent of the expression of ER alpha and beta, progesterone receptor (PgR) and HER2/neu in pregnancy- associated breast cancer. Material and Methods: Formalin-fixed, paraffin embedded tissues from 16 patients with pregnancy- associated breast cancer were used in this study. Immunostaining for ERalpha, ERbeta and PgR was performed using monoclonal antibodies against ERalpha, PgR (DakoCytomation) and against ERbeta (CHEMICON). The EnVision detection system was applied. Tumors were considered to be expressing receptors if a positive reaction (regardless of intensity) could be identified in at least 10% of cells. The HER-2 status was analyzed using HercepTest TM (IHC), and IHC 2+ results were confirmed with FISH test. Results: 44% of the tumors (7/16) were ERalpha and PgR positive. The expression of ERbeta protein was observed in 94% of pregnancy-associated breast cancers. As many as 50% of ERbeta positive tumors showed no expression of ERalpha. Further, 31% (5 of 16) of breast cancers were HER2/neu positive. Conclusions: This frequent expression of ERbeta in pregnancy-associated breast cancer may result from their prodifferentiative functions which increase during pregnancy and lactation. No significant financial relationships to disclose.