1.Department of Pathology, Beijing Obstetrics and Gynecology Hospital, Capital Medical University,　Beijing 100006; 2.Department of Pathology, Beijing Friendship Hospital, Capital Medical University,　Beijing 100050，China

Objective To determine the expression of p63 and CK5/6 in different breast intraductal proliferative lesions and its significance in the diagnosis.MethodsThe expression of p63 and CK5/6 in 368 breast lesions from 150 samples was analyzed by immunohistochemical staining.ResultsIn the normal breast tissues, the expression of CK5/6 existed in myoepithelial and luminal epithelial cells. Among the 35 general proliferative lesions, 33 of CK5/6 staining showed mosaic pattern and 2 displayed diffuse positive pattern. In the atypical proliferative lesions, insitu carcinoma, or infiltrating ductal carcinoma, the expression of CK5/6 was all negative except 6 cases. Among the 6 positive cases, 2 were negative in the expression for estrogen receptor (ER), progesterone receptor (PR), and CerbB2, which were consistent with the characters of basaloid carcinoma. The expression of p63 existed in benign and noninfiltrated malignant lesions, whereas the expressions of p63 and CK5/6 were negative in 3 cases of insitu carcinoma. In the infiltrated carcinoma, the expression of p63 was only seen in 3 cases（3/43）.Conclusion The staining patterns of p63 and CK5/6 display special features in different breast intraductal proliferative lesions, which are benefit to the diagnosis and differential diagnose of various hyperplasia lesions.