Metastatic transformation of benign breast adenomyoepithelioma

Adenomyoepithelioma of the breast is a rare tumor, having a bicellular pattern of proliferation which consists of epithelial and myoepithelial cells. Though generally considered a benign tumor, removal of the primary tumor may occasionally be followed by local recurrence and rarely distant metastasis. We describe a case of a 60-year-old woman with adenomyoepithelioma of the breast who developed lung, bone, and kidney metastases 5 years after removal of the primary tumor.