Abstract: Objective : To analyze the clinical characteristics, pathological diagnosis, treatment and prognosis of ma-lignant adenomyoepithelioma of the breast. Methods : The medical records of 5 patients with malignant myoep-ithelioma treated in our hospital from 1991 to 2007 were retrospectively reviewed. Results : The five caseswere all female and aged from 27 to 74 years, with an average of 53 years. All cases underwent surgery. According to the AJCC staging guideline, there was 1 case of stage I and 4 cases of stage II. The follow-up timeafter surgery ranged from 9 to 64 months, with an average follow-up time of 48 months. One patient died dur-ing the follow-up period. Two cases had recurrence and metastasis after surgery. One had recurrence in theipsilateral chest wall and axillary lymph nodes and suffered bone metastases. The other case had recurrenceat the original surgical incision at one month after local resection. The mean survival time was 46 months.The immunohistochemical analysis revealed that the myoepithelial component of the tumor was positive forS100 protein, Actin, SMA (smooth muscle actin) and Vimentin. The epithelial component of the tumor was pos-itive for different types of cytokeratins, EMA and AE1/AE3. However, most of the tumor was negative for ER,PR and C-erbB2. Conclusion : The epithelial or myoepithelial cellular component of breast adenomyoepithelialtumor can develop malignancies. Histology combined with immunohistochemistry can assist in the diagnosis.Treatment modalities include surgery, chemotherapy and radiotherapy. Patients with malignant adenomyoep-ithelioma of the breast may have recurrence and metastasis, which appear to be hematogenous rather thanlymphatic.