Diagnosis of an extremely rare case of malignant adenomyoepithelioma in pleomorphic adenoma: A case report

BACKGROUND: Pleomorphic adenoma (PA) is the most common type of salivary gland tumor, and its common sites are parotid gland, sinus, nasal septum and cleft palate. PA is an uncommon benign type of tumor occurring in the breast, and there are few reports of cases in Asia. CASE SUMMARY: An 84-year-old woman found a mass in the upper outer quadrant of the right breast > 1 year ago. The patient underwent a right breast lumpectomy and sentinel lymph node biopsy. The pathological diagnosis was PA in the upper outer quadrant of the right breast, and the malignant component was malignant adenomyoepithelioma. The postoperative course was uneventful, and no chemotherapy was administered. At 18 mo of follow-up, the patient is alive and well, with no evidence of recurrent disease. CONCLUSION: Patients with breast PA should first undergo extended excision of breast masses followed by pathological examination. If malignancy is confirmed or the surgical margin is positive, modified radical mastectomy should be performed.