MYOEPITHELIAL CARCINOMA OF THE BREAST WITH DISTANT METASTASIS AND ACCOMPANIED BY ADENOMYOEPITHELIOMAS

A breast tumour in a 47-year-old female with axillary lymph node metas tasis was interpreted as the rare malignant adenomyoepithelioma based on morphological and immunohistochemical studies. Multiple bone metast ases developed and the patient died after 7 months. The malignant neop lasm consisted of cords and interlacing bundles of spindle cells with indistinct cell borders and clear cytoplasm. The cells stained positiv ely for cytokeratin, S-100 protein, GFAP, and muscle-specific actin, a nd possessed basal lamina, pinocytic vesicles, tonofilaments, desmosom es, and intermediate filaments with dense bodies. In some areas, cells with microvillous projections enclosed small spaces. In the breast, f oci of myoepithelioma with various morphological subtypes and infiltra tion coexisted, demonstrating the origin of the malignant tumour. The histogenesis of the myoepithelial tumours is discussed.