Adenomyoepithelioma of the breast is an uncommon
tumor characterized by dual differentiation into
luminal cells and myoepithelial cells. A spectrum of histologic patterns is observed among these
tumors and even in different areas of individual
tumors. These lesions can be diagnostically challenging, especially when a core needle biopsy is performed, because of the heterogeneity of
adenomyoepitheliomas. Recognition of the biphasic cellular elements and the characteristic overall architecture of the
tumors in combination with immunohistochemistry are essential to establish the correct diagnosis. Although most
tumors have a benign
clinical course, local recurrences, malignant transformations, and distant
metastases have been reported. All the reported malignant
adenomyoepitheliomas with
metastases have shown significant cytologic atypia and brisk mitotic rates. Therefore, adequate sampling of the
tumor to identify these features is necessary. A complete excision with adequate margins would lower the chance of local recurrence or potential for
metastasis.