Objective: The aim of our study was to observe the expressions and clinical Significance of E-cadherin, β-catenin and E-cadherin-catenins complex in breast cancer and precancerous lesions, and analyze the relationship between the expressions and clinicopathological features in breast cancer. Methods: Immunhistochemical UltraSensitiveTM S-P method was employed to detect the expression of E-cadherin, β-catenin and E-cadherin-catenins complex in 128 cases of invasive ductal carcinomas, 89 cases of ductal carcinoma in situ and 57 cases of atypical ductal hyperplasia, 53 cases of usual ductal hyperplasia breast tissues were selected as a control group. The express of E-cadherin, β-catenin and their relationship with mult biological parameters including histological grade, region lymph node metastasis, distant metastasis and recurrence on files were also assessed. Results:(1) The staining patterns character of E-cadherin, β-catenin and E-cadherin-catenins complex: In UDH breast tissues, E-cadherin and a-catenin were expressed on cell membrane of ductal and acinic cells, showing cellular contour and border among cells. The abnormal expression of the three proteins occurred in breast invasive ductal carcinomas, ductal carcinoma in situ and atypical ductal hyperplasia tissues, showing cytoplasmic or nuclear staining, decrease and loss of cytomembrane staining.(2) The abnormal expression rates of E-cadherin, β-catenin and E-cadherin-catenins complex in invasive ductal carcinomas were 53.91%, 65.63% and 81.25%, which were significantly higher than that in ductal carcinoma in situ, atypical ductal hyperplasia, usual ductal hyperplasia tissues(P < 0.01). Compared with usual ductal hyperplasia breast tissues group, the abnormal expression rates of E-cadherin, β-catenin and E-cadherin-catenins complex were significantly decreased(P < 0.01) in the breast cancer group. However, there was no significance of the abnormal expression rate between ductal carcinoma in situ and atypical ductal hyperplasia tissues groups(χ2 = 0.76, P = 0.38; χ2 = 0.14, P = 0.70; χ2 = 0.81, P = 0.37; χ2 = 2. 19, P = 0.14)(P > 0.05).(3) There was a significantly difference in the mean E-cadherin, β-catenin and Ecadherin-catenins complex frequency between estrogen receptor & progesterone receptor positive IDC group and negative group, epidermal growth factor receptor type 2(HER2/neu) positive and negative groups, Ki-67 proliferation index ≤ 14% and > 14% groups, histological grade(I + II) and grade III invasive ductal carcinomas groups, with lymph node metastasis, distant metastasis and recurrence groups(P < 0.05) and without groups(P < 0.05). However, there was no difference in the mean E-cadherin, β-catenin and E-cadherin-catenins complex frequency between age(≤ 50 years vs > 50 years), tumor diameter(≤ 2 cm vs > 2 cm)(P > 0. 05). Conclusion: In breast cancer, the expressions of E-cadherin, β-catenin and E-cadherin-catenins complex are abnormally decreased and are correlated with pathology grade, differentiation disturbance and metastasis. Ecadherin and β-catenin may be as the predictors for prognosis. Combined detection may improve accuracy and sensitivity of predicting metastasis and prognosis of breast Cancer. Objective: The aim of our study was to observe the expressions and clinical Significance of E-cadherin, β-catenin and E-cadherin-catenins complex in breast cancer and precancerous lesions, and analyze the relationship between the expressions and clinicopathological features in breast cancer . Methods: Immunhistochemical UltraSensitive ™ SP method was employed to detect the expression of E-cadherin, β-catenin and E-cadherin-catenins complex in 128 cases of invasive ductal carcinomas, 89 cases of ductal carcinoma in situ and 57 cases of atypical ductal hyperplasia , 53 cases of usual ductal hyperplasia breast tissues were selected as a control group. The express of E-cadherin, β-catenin and their relationship with mult biological parameters including histological grade, region lymph node metastasis, distant metastasis and recurrence on files were also assessed. (1) The staining patterns character of E-cadherin, β-catenin and E-cadherin-catenins complex: In UDH breast tissues, E-cadherin and a-catenin were expressed on cell membrane of ductal and acinic cells, showing cellular contour and border among cells. The abnormal expression of the three proteins occurred in breast invasive ductal carcinomas, ductal carcinoma in situ and atypical ductal hyperplasia tissues, (2) The abnormal expression rates of E-cadherin, β-catenin and E-cadherin-catenins complex in invasive ductal carcinomas were 53.91%, 65.63% and 81.25%, which were significantly higher than that in ductal carcinoma in situ, atypical ductal hyperplasia, usually ductal hyperplasia tissues (P <0.01). Compared with usual ductal hyperplasia breast tissues group, the abnormal expression rates of E-cadherin, β-catenin and E-cadherin -catenins complex were significantly decreased (P <0.01) in the breast cancer group. However, there was no significance of the abnormal expression rate between ductal carcinoma in situ and atypi cal du(3) There was no significant difference between the two groups (χ2 = 0.76, P = 0.38; χ2 = 0.14, P = 0.70; a significant difference in the mean E-cadherin, β-catenin and Ecadherin-catenins complex frequency between estrogen receptor & progesterone receptor positive IDC group and negative group, epidermal growth factor receptor type 2 (HER2 / neu) positive and negative groups, Ki- 67 proliferation index ≤ 14% and> 14% groups, histological grade (I + II) and grade III invasive ductal carcinomas groups, with lymph node metastasis, distant metastasis and recurrence groups (P <0.05) . However, there was no difference in the mean E-cadherin, β-catenin and E-cadherin-catenins complex frequency between age (≤ 50 years vs> 50 years), tumor diameter (≤ 2 cm vs> 2 cm) > 0.05). Conclusion: In breast cancer, the expressions of E-cadherin, β-catenin and E-cadherin-catenins complexes are abnormally decreased and are correlated with pathology grade, differentiation disturbance and metastasis. Ecadherin and β-catenin may be as the predictors for prognosis. Combined detection may improve accuracy and sensitivity of predicting metastasis and prognosis of breast cancer.