Malignant adenomyoepithelioma combined with adenoid cystic carcinoma of the breast: a case report and literature review

Background: Malignant adenomyoepithelioma and adenoid cystic carcinoma are both rare malignant epithelial-myoepithelial tumors of the breast. We report a very rare case with a malignant adenomyoepithelioma combining with adenoid cystic carcinoma in a single mass. Case presentation: A 61-year-old female presented with a palpable painless mass in the right breast. Mammography revealed a large irregular dense shadow without obvious internal calcification. A simple lumpectomy was performed, and a 1.6cm well-circumscribed pale-tan nodule was presented. Histologically, the nodule was composed of two obscure lobules. One exhibited typical histological image of adenoid cystic carcinoma, the other one showed the image of epithelial-myoepithelial carcinoma of salivary gland, and support the diagnosis of biphasic malignant adenomyoepithelioma. Transition between the two lobules was gradual. Immunohistochemically, CK18 and P63 highlighted the epithelial and myoepithelial cells respectively in both lesions. CD117 was positive in the epithelial cells of adenoid cystic carcinoma, but was totally negative in malignant adenomyoepithelioma. Conclusion: This report is, to our knowledge, the first case that combines these two tumors in a single mass. In addition, we present a review of the literature. The histogenesis of these tumors is also discussed.