Clinically aggressive metastasizing pleomorphic adenoma: report of two cases.

BACKGROUND: It has been suggested that metastasizing pleomorphic adenomas may represent unrecognized malignancy.

METHODS: The cytologic and clinical characteristics of two metastasizing pleomorphic adenomas diagnosed by fine-needle sampling are reported.

RESULTS: Both showed malignant evolution: the primary tumors arose from the palate and the parotid salivary glands, respectively. Metastases occurred simultaneously with local recurrence in the first patient and after a second local recurrence in the second patient. Both patients were treated by surgery and radiotherapy but died of disseminated disease 8 and 4 years after initial diagnosis. No histologic evidence of malignancy was observed on cytology smears or histology sections in either case.

CONCLUSION: Clinically, our cases support the hypothesis that metastasizing pleomorphic adenomas represent unrecognized malignancy, because the biologic course of two tumors led to unequivocally lethal outcome.