Aims: Apocrine carcinoma of the breast seldom expresses oestrogen receptors (ER) or progesterone receptors (PR), but frequently expresses androgen receptors (AR). Because of this unusual hormone receptor status, it has been suggested that oestrogens have a less important role in the pathogenesis of apocrine carcinoma. The ER status of apocrine carcinoma has been studied for one kind of ER, the classic receptor now named ER-α; however, the status of ER-β, a secondary oestrogen receptor, has not been examined systematically in apocrine carcinoma. The aim was to study ER-β status in apocrine carcinoma.
Methods and results: The expression of ER-β was examined immunohistochemically in 48 apocrine carcinomas and compared with clinicopathological factors and ER-α, PR and AR status. ER-β positivity was observed in 35 cases (73%), regardless of any clinicopathological factors or the status of other receptors. The results of ER-β mRNA analysis supported the immunohistochemical results.
Conclusions: The significance of oestrogens in apocrine carcinoma should not be dismissed at present when the role of ER-β remains to be determined. Studying the action of oestrogen or antioestrogen in apocrine carcinoma may reveal a role for ER-β independent of ER-α and raise the potential of hormonal therapy for these tumours.