Metastasis of benign pleomorphic adenoma

Metastasizing pleomorphic adenoma (MPA) of salivary glands are rare tumors that inexplicably metastasize to distant sites and display benign histological features in both the primary tumor as well as in the metastatic deposits. This metastasis of benign PA is most often seen after having previous local recurrence (either single or multiple). The most common metastatic sites are reported to be bone, lung, and cervical lymph nodes. Currently, no histologic or molecular parameters exist that can predict the development of metastasis in these neoplasms. This case reviews the current literature on MPA and describes a 73-year-old male with original diagnosis of benign PA from the left parotid gland with metastasis to the liver 8 years later without local recurrence.