Metachronous bilateral pleomorphic adenoma of the parotid gland.

Bilateral salivary gland tumors are very rare, accounting for 3% of all parotid gland tumors. Although the most common tumor with bilateral development is the Warthin tumor, pleomorphic adenomas (PA) have been diagnosed simultaneously as well, but in a smaller incidence. Because of this, the prevalence, etiology, pathogenesis, and behavior of the PA in this context are poorly understood. We present a case of bilateral metachronous PA affecting the parotid gland in a 63-year-old woman. Clinically, the lesions presented with similar aspects as seen in cases of solitary PA with slow-growing asymptomatic nodule. Both lesions were diagnosed by fine-needle aspiration biopsy at an interval of 2 years between them. A total and superficial parotidectomy for left and right tumors, respectively, was performed. Only on the left side some facial nerve branches were removed that induced partial paralysis in the patient. A review of the pertinent literature is included.