Estrogen receptor β

Abstract

Context.-A new class of estrogen receptors was discovered in 1996 and named estrogen receptor β (ER-B); the traditional estrogen receptor, which until a little more than 10 years ago was thought of as the only estrogen receptor in existence, is now called estrogen receptor α. Estrogen receptor β has at least 5 isoforms, which may have different functions and have different tissue distribution. The significance of ER-B expression in tumors was first demonstrated in breast cancer, with several studies demonstrating that women with ER-B-positive breast cancers treated with adjuvant tamoxifen have better survival, independent of estrogen receptor a expression. Pathologists need to be more aware of this increasingly important protein, as it will soon find its way into routine clinical practice. Objective.-To provide pathologists with a concise review of ER-B, with special emphasis on current and potential clinical relevance. Data Sources.-A search of the English literature in PubMed (National Library of Medicine, Bethesda, Maryland) for articles with titles including "estrogen receptor beta," with emphasis on "immunohistochemistry. " Abstracts were reviewed, and selected articles were used as the basis for writing this review, mostly based on their relevance to pathology. Conclusions.-Estrogen receptor β and its isoforms have wider tissue distribution, including the gastrointestinal tract, lung, and brain, than the traditional estrogen receptor, now called estrogen receptor α. Estrogen receptor β expression in breast cancer is associated with favorable outcome in women treated with adjuvant tamoxifen, even in tumors negative for estrogen receptor α. The clinical significance of ER-B expression in tumors other than breast is currently under investigation.