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

## TL;DR

A rare case of a benign tumor and breast cancer occurring together in the same breast is reported, highlighting diagnostic and treatment challenges.

## Contribution

This case report adds to the limited literature on coexisting pleomorphic adenoma and ductal carcinoma in the mammary gland.

## Key findings

- A 70-year-old woman had a benign pleomorphic adenoma and ductal carcinoma in situ diagnosed in the same breast.
- Surgical resection with a narrow margin was performed, and the resection margin was found to be sufficient.
- The case highlights the difficulty in distinguishing pleomorphic adenoma from other similar breast tumors.

## Abstract

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.

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.

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.