A Case of Pleomorphic Adenoma and Ductal Carcinoma In Situ in the Same Mammary Gland.

Introduction: Pleomorphic adenoma is a benign tumor that frequently occurs in the salivary glands; however, it occurs in the breast rarely. There have been few reports of breast cancer complicated by pleomorphic adenoma of the mammary gland.

Case presentation: A 70-year-old woman was found to have a mass lesion in her left breast during a medical examination. A needle biopsy was performed, and a diagnosis of pleomorphic adenoma was made. We performed a partial mastectomy with a margin of several millimeters from the tumor. Pathological examination revealed a diagnosis of pleomorphic adenoma with ductal carcinoma in situ. The resection margin was sufficient, and the patient was followed up.

Conclusions: Pleomorphic adenoma arising in the mammary gland is difficult to differentiate from adenomyoepithelioma, mucocele-like tumor, and metaplastic carcinoma. Since the tumor can become malignant, resection with a narrow margin is recommended, along with special efforts not to damage the capsule at diagnosis.