A case of adenomyoepithelioma with myoepithelial carcinoma of the breast

Normal breast tissue consists of branching ductal networks that are lined by an outer layer of myoepithelial cells and an inner layer of polarized ductal epithelium.1 Breast myoepithelial cells are usually located between the basement membrane and breast ductal epithelium.2 Based on the World Health Organization classification of tumors of the breast, the myoepithelial lesions are composed of a pure or dominant population of myoepithelial cells, while the epithelial‐myoepithelial lesions are derived from a dual population of epithelial and myoepithelial cells.3 Epithelial‐myoepithelial lesions include pleomorphic adenomas, adenomyoepitheliomas (AMEs), AME with carcinoma, and adenoid cystic carcinomas.3 Adenomyoepitheliomas is characterized by the bicellular proliferation of glands that consist of an inner epithelial and an outer myoepithelial layer of cells.4 It can have a spindle, tubular, or lobulated histological pattern.5 One or both of the components of the tumor may exhibit malignant transformation, which is called AME with carcinoma and is characterized by a higher mitotic rate, infiltrative growth pattern, marked cytologic atypia, necrosis, and/or metastasis of cells.5 Adenomyoepitheliomas with myoepithelial carcinoma of the breast is rare, and its biological behavior and treatment are not well characterized. This report presents a case of AME with myoepithelial carcinoma of the breast.