Objective: Alteration of phosphatase and tensin homolog (PTEN) and metalloproteinase-9 (MMP-9) expression is involved in carcinogenesis, and both proteins are correlated with malignant cell invasion and metastasis. This study focused on PTEN and MMP-9 expression in the invasive micropapillary carcinoma (IMPC) of the breast and its relationship to clinical pathological features. Materials and Methods: The immunohistochemical S-P method was used to detect the expression levels of PTEN and MMP-9 in 49 cases of IMPC (the proportion of IMPC in breast carcinoma is approximately 5-100%) and 30 cases of normal breast tissue. Results: In IMPC, PTEN, and MM-9 expression levels were negatively and positively related, respectively, to the histopathologic grade and lymph node metastasis (both p < 0.05). The PTEN expression was negatively related to MMP-9 expression (p < 0.05). Conclusion: These results suggest that lack of MMP-9 and PTEN overexpression are early markers of breast carcinogenesis preceding tumor invasion. Apparently, IMPC carries the risk of progression to a malignant phenotype according to these markers. The clinical importance of these finding is discussed.