Malignant Adenomyoepithelioma of the Breast

ABSTRACT

An adenomyoepithelioma of the breast is an uncommon tumor that is characterized by biphasic lesions, which consist of epithelial and myoepithelial cells. Most adenomyoepitheliomas are benign, and a malignant transformation is rare. It is generally limited to the epithelial component but in rare cases, the myoepithelial component may become malignant and give rise to a malignant myoepithelioma. We encountered a case of a 29-year-old woman who presented with both an epithelial and myoepithelial carcinoma of the breast in an adenomyoepithelioma. The malignancy was evidenced by the presence of pleomorphism, a high mitotic rate and local invasion. Immunohistochemical staining demonstrated the expression of cytokeratin in epithelial cells and actin in myoepithelial cells. We report this case of a malignant adenomyoepithelioma of the breast with review of the relevant literature.