Metastasizing pleomorphic adenoma of the salivary gland

A case of metastasizing pleomorphic adenoma in which both the primary tumor and metastasis were composed of benign pleomorphic structures is reported and previously reported cases reviewed. The metastasis commonly developed many years after the excision of the primary tumor and was usually preceded by local recurrences. The most common sites of metastasis were the bone and lung. Mitotic activity and infiltrative growth pattern are the histologic features in the primary tumor important in predicting the metastasizing potential. The treatment of choice for the metastatic tumor appears to be surgical excision. Radiotherapy seems to have a limited role other than providing temporary palliation.