Adenomyoepitheliomas (AMEs) are rare, biphasic neoplasms containing both luminal epithelial cells and myoepithelial cells (1-5). They exist in the spectrum of biphasic breast neoplasms, which also include pleomorphic adenomas and adenoid cystic carcinomas (1-5). These neoplasms typically present as a painless breast mass, with the average age of diagnosis in the 60th decade (1-5). These neoplasms can also rarely occur in men (6). As in normal breast parenchyma, the luminal epithelial cells of AMEs stain with epithelial immunohistochemical stains, such as cytokeratin 7 and epithelial membrane antigen, whereas the myoepithelial cells stain with myoepithelial markers, such as p63, S-100, and smooth muscle myosin heavy chain (1-6).
They typically exhibit benign behavior but either the epithelial or mesenchymal components can undergo malignant transformation into an epithelial carcinoma, a myoepithelial carcinoma, or an epithelial-myoepithelial carcinoma (1-7). Malignant AME is a synonym for AME with carcinoma. Histologic evidence of malignancy includes cellular pleomorphism, mitotic activity, necrosis, overgrowth of either myoepithelial or epithelial component and invasion at the periphery of the tumor (8). The majority of AMEs can be treated by local excision, even though local recurrence may occur. In some cases, metastases to lymph nodes and to the lungs have been reported (6,7). A carcinoma arising in a malignant AME should be managed as any other type of breast carcinoma of similar grade and stage.
The patient had subsequent sentinel axillary lymph node biopsies, which showed benign lymph nodes. She underwent adjuvant chemotherapy with four cycles of adriamycin and cyclophosphamide with pegfilgrastim, followed by weekly paclitaxel, which she tolerated well.
Contributed by Terri E. Jones, MD and Jing Yu, MD, PhD