Abstract
Adenomyoepithelioma (AME) is a benign tumor characterized by biphasic proliferation of both epithelial and myoepithelial cells, and in some cases can become malignant. We report 2 cases of malignant AME of the breast.
Case 1 was a 68-year-old woman. A tumor was located in the right breast, measuring 14 mm in diameter. The tumor appeared as a lobulated mass. Core needle biopsy revealed both AME and ductal carcinoma, suggesting a coexistence between both lesions. Partial resection was performed. Microscopically, the epithelial cells of the AME had become malignant and we diagnosed the tumor as an AME with ductal carcinoma in situ (DCIS).
Case 2 was an 81-year-old woman with a tumor located in the right breast, measuring 35 mm in diameter. The tumor appeared as an irregularly-shaped mass. Core needle biopsy revealed a malignant AME ; a malignant phyllodes tumor was also suspected. A mastectomy with axillary lymph node dissection was performed. Microscopically, the myoepithelial cells of the AME had become malignant. Three months after the operation, radiology showed multiple lung, liver and bone metastases, and the patient subsequently died 6 months later.
AME is difficult to diagnose by core needle biopsy and the prognosis of malignant AME is very poor. Surgical biopsy should be performed for definitive diagnosis. It is important to resect the tumor before it starts growing.
