Adenomyoepithelioma of the Breast

Abstract

Adenomyoepithelioma of the breast is a rare benign breast neoplasm characterized by biphasic proliferation of epithelial and myoepithelial cells. It occurs in older women and presents as a palpable nodular mass. Mammographic findings are nonspecific and often suspicious for malignancy. A core needle biopsy may be misleading and may be mistaken for invasive ductal carcinoma. Characteristic histologic features include a well-circumscribed multinodular growth pattern, in which the nodules consist of closely intermixed proliferating glands and myoepithelial cells. Both epithelial and myoepithelial components show only mild pleomorphism and a low mitotic rate. The epithelial cells react with antibodies to cytokeratins. The myoepithelial cells show positive staining for smooth muscle actin, smooth muscle myosin, calponin, p63, desmin, and S-100. Incompletely resected tumors or tumors extending to the resection margins tend to recur. Malignant transformation of adenomyoepitheliomas has been described but occurs rarely.