Objective:To study the relationship between expressions of α-,β-catenins and cyclin D1 and the occurrence, infiltration and metastasis of breast cancer. Methods: High sensitive S-P immunohistochemical method was used to detect the protein expressions of α-,β-catenins and cyclin D1 in the 60 cases of breast cancer tissues. Results: Abnormal immu-noreactivities of α-and β-catenins were observed in 37 (61.7%) and 42 (70%) cases of breast cancer tissues, respectively. There were 28 cases (46.7%) who showed cyclin D1 overexpression. The abnormal expression rates of α-and β-catenins in infiltrating lobular carcinoma (ILC) were significantly higher than those in infiltrating ductal carcinoma (IDC) (P<0.05), but they had no relations to the extent of differentiation and lymphatic metastasis of breast cancer (P>0.05). The overexpression rate of cyclin D1 was correlated with tumor stage and lymphatic metastasis of breast cancer (P<0.05), but not with histological type and the extent of differentiation (P>0.05). Cyclin D1 overexpression was observed in 57.1% (24/42) of these cases that showed abnormal staining of β-catenin, but only observed in 22.2% (4/18) of these cases with normal membranous staining of β-catenin. There was a significantly positive correlation between the abnormal expression of β-catenin and overexpression of cyclin D1 (rs=0.321, P<0.05). Conclusion: The abnormal expression of β-catenin may play an important role in the genesis of breast cancer by triggering cyclin D1 overexpression in breast cancer. The abnormal expressions of α-and β-catenins are not a key factor in malignant cell metastasis in breast cancer, but may also involve in the progress. Methods: High sensitive SP immunohistochemical method was used to detect the protein expressions of α-, β-catenins Results: Abnormal immu-noreactivities of α-and β-catenins were observed in 37 (61.7%) and 42 (70%) cases of breast cancer tissues, respectively. There were 28 The abnormal expression rates of α-and β-catenins in infiltrating lobular carcinoma (ILC) were significantly higher than those in infiltrating ductal carcinoma (IDC) (P <0.05), but they had no relations to the extent of differentiation and lymphatic metastasis of breast cancer (P> 0.05). The overexpression rate of cyclin D1 was correlated with tumor stage and lymphatic metastasis of breast cancer (P <0.05), but not with histological type and the extent of d (P> 0.05). Cyclin D1 overexpression was observed in 57.1% (24/42) of these cases that showed abnormal staining of β-catenin, but only observed in 22.2% (4/18) of these cases with normal membranous staining of β-catenin. There was a significant positive correlation between the abnormal expression of β-catenin and overexpression of cyclin D1 (rs = 0.321, P <0.05). Conclusion: The abnormal expression of β-catenin may play an important role in the genesis of breast cancer by triggering cyclin D1 overexpression in breast cancer. The abnormal expressions of α-and β-catenins are not a key factor in malignant cell metastasis in breast cancer, but may also involve the progress.