Abstract: Objective: To investigate the expression and significance of tumor suppressor gene PTEN in axillary node negative breast cancer and to analyze the relationship between PTEN and microvessel density(MVD). Methods: Eighty-one cases of breast cancer and 20 cases of corresponding adjacent tissues were performed by immunohistochemical staining (S-P) for the expressions of PTEN and CD34, as well as MVD. Results were compared with the clinical pathologic parameters and patients' survival. Results: The positive expression rate of PTEN in breast cancers(67.4%) was significantly lower than that of adjacent tissues (95.8%). Loss of PTEN was significantly associated with tumor grade, ER status, recurrence and distant metastasis. The 5 years survival rate of PTEN positive group was significantly higher than that of PTEN negative group. PTEN expression significantly negative correlated with MVD (r=-01511, P0101). Conclusions: Loss of PTEN protein is a common event in LNN breast cancer and may play an important role in tumor angiogenesis. Patients with negative PTEN and high MVD have a short survival. Detection for expression of PTEN and MVD is helpful to evaluate the prognosis of patients with axillary node negative breast cancer.