Benign and malignant parotid pleomorphic adenomas: CT and MR studies.

Parotid pleomorphic adenomas are usually benign, solitary, ovoid masses. Occasionally, these tumors may be highly lobulated and clinically mimic multiple lesions. Actual multiple benign mixed tumors are rare as are malignancies that occur in these pleomorphic adenomas. Of these malignancies, the most common type is the carcinoma ex pleomorphic adenoma. Two patients are presented, one of whom had a markedly lobulated benign mixed tumor and the other patient had an ex pleomorphic malignancy associated with multiple benign mixed tumors. Both cases are documented with CT and magnetic resonance studies. The relative merits of these modalities are discussed as they apply to these parotid masses.