To verify the difference of estrogen receptor β ERβ) expression between breast cancer and normal mammary tissue and the roles of ERβ in prognosis of breast cancer, its expression was investigated in normal mammary and breast cancer tissues.

The ERβ expression of 89 normal mammary and 100 breast cancer tissues was examined using immunohistochemistry. The staining signal was scored by estimating the proportion (range, O-5)and intensity scores(range, O-3) of positive cells. The ERβ expression was considered as positive if the total score (IHC score; range, O-8) was 3 or more. The ERβ expressions were compared between normal mammary and breast cancer tissues. The association of ERβ expression with other clinicopathological factors was also investigated. The distant relapse free survival(DRFS) and overall survival(OS) rates were compared according to the ERβ expression.

Eighty-eight of the 89 (98.9%) cases of normal mammary tissues and 74 of the 89(83.1%) counterpart breast cancer tissues showed positive staining with decreased ERβ expression in the breast cancer compared to the normal mammary tissue with statistical significance (p=0.026). In breast cancer, the ERβ expression was found to have a positive correlation with the ER expression but with only marginal significance (p=0.063). There was no correlation between the ERβ expression and other clinicopathological factors (age, tumor size, nodal status, histological grade, progesterone receptor status, and HER-2 expression). The 5 year DRFS and OS rates were found to be independent of ERβ expression.

The ERβ expression was significantly decreased in cancer tissues. Further study with a sufficient number of patients is needed to verify the roles of ERβ during breast cancer carcinogenesis and clinical value.