Estrogen receptor beta expression in invasive breast cancer

The aim of this work was to determine the extent of estrogen receptor beta (ER-β) expression in invasive breast cancer (BrCA) and whether ER-β expression is correlated with response to adjuvant hormonal therapy with tamoxifen (AHTT). Immunohistochemical staining (IHC) for estrogen receptor alpha (ER-α) and ER-β was performed on sections of formalin-fixed and paraffin-embedded tissue from 47 unselected invasive breast carcinomas (BrCA). IHC for ER-β was also performed on sections of BrCA from 118 women who were treated with mastectomy and AHTT. Survival analysis was performed using the Kaplan-Meier method and the log-rank test. Of the 47 unselected BrCA, 17 (36%) were negative for ER-α and of these, 8 (47% of ER-α negative cases and 17% of all 47 patients) were ER-β positive. Five of the 8 ER-α negative and ER-β positive cases were positive for ER biochemically. There was no correlation between ER-β positivity and overall survival in the unselected group. By contrast, in the group of women treated with AHTT, expression of ER-β in more than 10% of cancer cells was associated with better survival (P =.0077), even in women with node-negative BrCA (P =.0069). In conclusion, our results show that a significant number of women with BrCA are positive for ER-β only, and may be determined to be ER-negative when currently available IHC is used. ER-β status is a significant predictor of response to AHTT in women with BrCA. Larger studies with multivariate analysis are needed to confirm these findings. HUM PATHOL 32:113-118. Copyright © 2001 by W.B. Saunders Company