Abstract: Objective 　To research the expression of the novel hyperplasia suppressor gene ( HSG) and mat rix metalloproteinase23 (MMP23) in different breast tissues. Methods 　Immunohistochemist ry method was used to measure the expression of HSG and MMP23. Fif ty2eight cases were breast cancer samples, thirty2three cases were breast fibroadenoma samples, thirty cases were breast hyperplasia and fif teen sam2 ples of normal breast tissues. All these cases were collected up f rom the department of pathology of the Tangshan Worker' s Hospital. Results 　The positive rate of HSG and MMP23 was 44. 83 %(26/ 58) and 84. 48 %(49/ 58) in breast cancer tissues respectively. The positive expression rate of HSG was compared between normal breast group and breast fibroadenoma group, the expression rate of HSG decreased sig2 nificantly, MMP23 increased in the breast cancer group ( P < 0. 05) ; the low level of HSGin breast cancer was correlated with lymph node metastasis ( P < 0. 05), was not correlated with the tumor size, age clinical pathological grade. The high level of MMP23 was not associated with the tumor size and lymph node me2 tastasis. On the other hand, there were not clear correlation between HSG and MMP23 in breast cancer, breast hyperplasia, breast fibroadenoma and normal breast tissues. Conclusion 　The expression rate of HSG and MMP23 was not equal in different breast tissues. It indicated that there was a close relationship between HSG,MMP23 and the occurrence and development of breast cancer.