[Breast myoepithelioma. Report of a case].

Myoepithelial cell tumors of the breast are rare. They present diagnostic difficulties not only on frozen sections but also after fixation and paraffin embedding. These tumors can give rise to a wide range of clinical evolution... Treatment vary from simple excision for myoepitheliosis to mastectomy with axillary node dissection for malignant myoepitheliomas. Large excision is necessary for adenomyoepitheliomas because of the risk of recurrence and, more uncommonly, their proclivity to metastasis. We report the case of breast myoepithelioma in a 42 years old woman. The tumor was clinically, radiologically and macroscopically well demarcated. Histologically the tumor was composed of myoepithelial cells with few cellular atypias and a low mitotic activity. Tumor cells expressed vimentin, actin, S100 protein and cytokeratin. This particular immunohistochemical phenotype allows the differential diagnosis with other breast tumors.