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.