Adenomyoepithelioma of the breast.

This report describes an additional case of adenomyoepithelioma, a rare neoplasm of the breast. The tumor presented as a well-defined mass and, cytologically, appeared to be benign. Histologically, the tumor demonstrated the characteristic bicellular differentiation of luminal epithelial and myoepithelial cells reported in previous adenomyoepitheliomas of the breast. On the basis of histological and immunological features, this tumor appeared to be the counterpart of the clear-cell (glycogen-rich) adenoma and epithelial-myoepithelial carcinoma of the salivary glands.