Clinicopathological Characteristics of Estrogen Receptor‐(3‐positive Human Breast Cancers

Recent studies have identified the presence of estrogen receptor (ER)‐β in addition to ER‐α in human breast cancers, but the Clinicopathological characteristics of ER‐β‐positive tumors remain to be established. In this study, we have conducted an immunohistochemical analysis of ER‐α and ER‐β expression in human breast cancers. In addition, we investigated the correlation of ER‐α and ER‐β expression with progesterone receptor (PR) status, determined by enzyme immunoassay, and with various Clinicopathological factors. Of 79 tumors, 49 (62%) were positive for ER‐α and 24 (30%) were positive for ER‐β, and there was no significant association between ER‐α and ER‐β expression. ER‐α‐positive tumors were significantly more likely to be PR‐positive than were ER‐α‐negative tumors (P<0.0001), but there was no significant association between ER‐β expression and PR status. However, the PR values of ER‐α‐positive and ER‐β ‐positive tumors (65±17 fmol/mg protein, mean±SE) were marginally significantly lower than those of ER‐α‐positive and ER‐β ‐negative tumors (340±109) (P=0.08). ER‐β positivity was significantly associated with small tumor size (<2 cm) and high histological grade (P<0.05), and this association was also observed when only ER‐α‐positive tumors were considered. These results suggest that determination of ER‐β status might be clinically useful for further defining the characteristics of ER‐α‐positive tumors