Clinical History:

A 43-year-old woman has noticed a painless swelling on the left side of her face, increasing for over 2 years. When examined by her physician there is a 4 cm firm, mobile mass anterior to the lower left ear. The mass is excised.

Findings:

The appearance of the mass with MR imaging is shown (image 7.1). The low and high microscopic appearances of the mass demonstrate small clusters of cells in a chondroid matrix (images 7.2 and 7.3).

Questions:

1. What is the diagnosis?

Pleomorphic adenoma of the parotid gland This represents 65 to 80% of all parotid tumors.

2. What is the prognosis?

This is a benign neoplasm, and the most common location for it is in the parotid gland. These lesions are usually slow-growing, but can recur following incomplete resection. The facial nerve is often close to these neoplasms, and excision with grafting may be necessary. Carcinoma is present in about 2% of pleomorphic adenomas.

3. What is the differential diagnosis for this mass?

Warthin's tumors account for 5 to 10% of all parotid gland tumors. Mucoepidermoid tumors account for 5 to 10% of all tumors of the parotid. Acinic cell carcinomas are rate but can be locally aggressive.