Parotid neoplasms are quite diverse in terms of their histology and biologic behavior. As a group, they represent about 2% of all head and neck neoplasms, and parotid gland tumors account for 70 to 80% of all neoplasms of the salivary glands. Parotid neoplasms are usually benign (80% for adults), and the most common benign neoplasm is the pleomorphic adenoma (about 85%) in adults, whereas hemangiomas and lymphangiomas are the most common neoplasms in children. Malignant tumors are divided into low-grade and high-grade neoplasms. The low-grade category comprises (1) low-grade mucoepidermoid, (2) low-grade adenocarcinoma, (3) acinic cell carcinoma, (4) basal cell adenocarcinoma, and (5) terminal duct adenocarcinoma. The high-grade group includes intermediate and high-grade mucoepidermoid, (2) adenoid cystic, (3) carcinoma ex pleomorphic adenoma, (4) adenocarcinoma, (5) undifferentiated carcinoma, (6) salivary duct carcinoma, and (7) dedifferentiated acinic cell carcinoma.

Our understanding of salivary gland neoplasms has undergone considerable change over the past three decades and newer methods of tissue sampling and tissue processing have improved the ease and accuracy of diagnosis and have therefore helped us select more appropriate therapy. Fine-needle aspiration biopsy (FNAB) is still viewed by many as controversial, in terms of its value in the diagnosis and management of salivary gland neoplasms. A recent Scandinavian study1 provides a typical report of the findings of 218 patients whose FNAB was confirmed histologically after surgical excision. The benign lesions were diagnosed accurately with 76% sensitivity and 83% specificity. FNAB was not as helpful with malignant lesions, and only 26 of 47 FNAB samples were considered malignant (sensitivity = 55%), whereas there were 11 false-positive diagnoses for malignancy (92% specificity). Misdiagnosis resulted in a delay of therapy in some patients because of reliance on the FNAB report by physicians who did not understand the limitations of that study. FNAB accuracy is higher when the surgical pathologist is experienced in interpreting these results. It is common to find reports of approximately 85% accuracy for detecting malignant tumors, 80% accuracy for detecting benign lesions, and 90% accuracy for diagnosing pleomorphic adenoma. It is clear that FNAB can provide useful information that has value in planning therapy, but it should not be the sole basis for management decisions. It has been performed in large series of patients without major complications and, when it is used routinely, it is found to shorten the time required for diagnosis. One of the important benefits of FNAB is the opportunity to avoid unnecessary operative risk for patients who have benign parotid neoplasms but who are very poor candidates for surgery because of other general medical conditions.

Some surgeons have not found good support for the routine use of FNAB and have emphasized the low accuracy of this study in diagnosing malignant parotid neoplasms. They believe that FNAB should be considered only as a screening examination in view of the fact that pathologists generally have much greater difficulty reaching a definitive diagnosis with salivary gland tumors, even when they are given a large tissue specimen. They emphasize that superficial lobe parotidectomy should be considered the gold standard for diagnosis and that this procedure is essentially an excisional biopsy for diagnosis.²

Clearly, FNAB is not as useful in salivary gland neoplasia as it has been for squamous cell carcinoma and thyroid neoplasia, and the report cannot be relied on as definitive. The clinical value of FNAB is a function of the experience of the cytopathologist; it must be combined with the impression gained from other studies as well as the history and physical examination.³

At this point, some experts advocate the routine use of FNAB in evaluating all parotid neoplasms, emphasizing the diagnostic accuracy, rapidity, patient convenience, and cost-effectiveness of this study and feel that it is probably the single most important piece of information to be obtained.^{4, 5} Other experts advocate the use of FNAB only for three specific indications: (1) for patients who are poor surgical risks, (2) for patients with a history of previous malignancy/metastasis, and (3) for patients in whom it is difficult to determine whether the lesion is neoplastic or inflammatory.⁶

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