Abstract: ObjectiveTo explore the expressions of estrogen receptors α and β in introductal proliferative lesions and invasive carcinoma of the breast. MethodsImmunohistochemistry was used to determine the expressions of ER α and β in 11 cases of usual ductal hyperplasia(UDH), 7 atypical ductal hyperplasia(ADH), 23 ductal carcinomas in situ(DICS)（8 DCISⅠ,11 DCISⅡ,4 DCIS Ⅲ) and 11 invasive breast carcinomas（IBC）. ResultsThe expression level of ERα increased in UDH, ADH and low grade DCIS, while it decreased in high grade DCIS and IBC. The expression of ERα was higher in UDH than in DCIS（P<0.05）. The expression of ERβ decreased in the transformation from normal breast tissues to UDH, ADH, DCIS and IBC, and there were significant differences between normal breast tissues and ADH, DCIS, IBC, as well as among UDH and DCIS, IBC（P<0.05）. No correlation was found between the expressions of ER α and ERβ（P>0.05）. ConclusionsThe expressions of ER α and β are different in the transformation from introductal proliferative lesions to breast carcinoma, and they may act by different mechanisms in carcinogenesis.

Key words: Breast neoplasms, Introductal proliferative lesions, Receptor, estrogen