Metastasizing pleomorphic adenoma of the salivary gland.

Metastasizing pleomorphic adenoma of salivary glands is a group of rare tumors that are histologically identical to benign mixed tumors and that inexplicably metastasize. A review of the literature revealed that it usually occurs after multiple local recurrences, and the interval between diagnosis of primary pleomorphic adenoma and metastases ranges between 3 and 52 years. The most common site for metastasis is bone, followed by the head and neck and lung. No histologic or molecular parameters exist at the present time that could predict the development of metastasis in these neoplasms. Metastasectomy confers significant survival advantage over nonoperative treatment for localized and accessible metastases, but there is no definite treatment protocol available in cases of widespread metastases.