Erica R. Thaler

The patient presenting with a parotid mass most often relates a history, long or short, of asymptomatic, unilateral, and progressive swelling. Uncommonly, there may be associated symptoms of pain, facial weakness or paralysis, or trismus. These accompanying symptoms usually, but not always, portend a malignant diagnosis. Absence of these symptoms does not confer a benign diagnosis. The vast majority of parotid masses are neoplastic. There are some nonneoplastic processes that may present as discrete lumps and should be considered in the differential diagnosis.

The most helpful ancillary test in the evaluation of a parotid mass is fine needle aspiration (FNA) biopsy. With the caveat in mind that FNA must be done by an experienced cytologist, it is ~85 to 90% accurate in making a histologic diagnosis. This can be quite helpful in treatment planning. Imaging, either computed tomography (CT) or magnetic resonance imaging (MRI), is also useful for treatment planning, particularly in considering the extent of surgery and whether or not facial nerve sacrifice may be likely prior to resection of a parotid malignancy. Definitive diagnosis is confirmed by surgical resection.

Benign Neoplasms

Benign neoplasms comprise 85% of all parotid neoplasms and include the following:

Pleomorphic adenoma (benign mixed tumor): Most common of benign neoplasms, accounting for 53% of all parotid neoplasms. Pathology includes both an epithelial and a mesenchymal component. These tumors have incomplete encapsulation and pseudopod extension, therefore requiring wide surgical excision for margin, rather than “lumpectomy.”

Warthin tumor (papillary cystadenoma lymphomatosum): Second most common benign neoplasm, accounting for 28% of all parotid neoplasms. Pathology reveals a papillary epithelium, lymphoid stroma, and cystic spaces containing thick, mucoid material. These are most commonly found in older men and have a 10% rate of bilaterality.

Oncocytoma