Benign Metastasizing Pleomorphic Adenoma: A Case Report

Abstract

Pleomorphic adenoma (mixed tumor) is the most common neoplasm of the salivary gland. It is usually a benign, slow-growing and well-circumscribed tumor. However, there are rare reports of a subset of these tumors metastasizing to distant sites without undergoing malignant transformation. Here we describe a case of pleomorphic adenoma of the parotid gland that metastasied to the cervical lymph node coincidentally with similar appearance of the primary lesion in the ipsilateral parotid gland. Case Presentation: A 78-year-old male with right sided cervical lymph node and ipsilateral parotid mass from one year ago came to Imam Khomeini hospital. Physical examination, a painless firm mass was found within year, the parotid and lymph node of the neck concomitantly with no other organs abnormalities. A diagnosis of pleomorphic adenoma was made from completion parotidectomy and cervical lymphadenectomy. No histologic characteristic of malignancy were seen in either specimen; therefore a diagnosis of benign metastasizing mixed tumor was rendered. Discussion: Benign metastasizing pleomorphic adenoma is a rare and controversial but distinct clinical entity. Although the definition of the term benign precludes metastatic disease, these tumors do not demonstrate any malignant features yet metastasized to distinct sites. It remains to be determined whether this benign metastasizing pleomorphic adenoma is really low grade salivary malignancy.