Malignant adenomyoepithelioma of the breast: a case with distant metastases

Adenomyoepithelioma is thought to be a low-grade malignancy, and cases showing malignant behavior are rare. A massive breast tumor with skin invasion in a 60-year-old woman was diagnosed as malignant adenomyoepithelioma. Despite the tumor size and skin invasion, no axillary lymph node metastases were detected. Light microscopy showed proliferation of tubular structures composed of atypical epithelial and myoepithelial cells and occasional anaplastic cells with mitotic figures extending to the epidermis of the skin. Twenty-four months after the surgery the patient complained of dull pain in the right thigh, and was found to have bone, lung and mediastinal lymph node metastases. There was neither local recurrence nor axillary lymph node metastasis. Subsequent femur fracture was treated by osteotomy. Despite additional chemoradiotherapy, the patient died 43 months after the first operation. Our case and literature review indicated that this tumor tends to show hematogenous metastasis.