The carcinosarcomas of the breast are made of mesenchymal and malign epithelial elements are rare. In this case; the left mastectomy material was taken from a 50-years old female patient. In the sections of the mass, well circumscribed, pale white coloured hemorragic centered nodular tumor 10 cm. in diameter showed swollen cut surface and firm consistency. The tissue specimens were examined both on light microscope level by using histochemical and immunohistochemical staining methods and on electron microscope level. In histologic sections two components of carcinomatous nests and sarcomatous areas were recognized to constitute the tumoral tissue. Reticular bundles had surrounded tumoral cell groups in epitelial regions, while the bundles had been seen around each cell in other areas. Keratin immunoreactivity was present in epithelial tumoral cells but couldn't be found in sarcomatous ones. Also vimentin, desmin and actin couldn't be identified in two components of the tumoral tissue. But alpha-1 antitripsin was present in both sarcomatous and epithelial tumor cells, but especially in sarcomatous areas. Observing by electron microscope it was noticed that some of the tumoral cells had epithelial but the others had mesenchimal features. This case was interpreted as carcinosarcoma with its charecteristics and existence was discussed with the accompaniment of literature studies.