Adenoid cystic carcinoma ex pleomorphic adenoma of the parotid gland.

There is a considerable variation in the histologic subtype of epithelial malignancies among carcinoma ex pleomorphic adenomas (CXPA) and virtually any known carcinoma entity can develop. To our knowledge, adenoid cystic carcinoma (AdCC) ex PA is quite rare despite the fact that de novo AdCC is the fourth most common salivary gland malignancy. We describe a new case of AdCC ex PA in the parotid gland of a 62 year-old woman. In our patient, there was a short interval of time between parotidectomy and local recurrence and rapid development of distant metastases. Although most of the reported cases are considered low-grade, evidence is presented here that AdCC can take the form of a high-grade malignancy in PA.