[Surgery of benign tumors of the parotid gland: the value of fine needle aspiration cytology]

Abstract

Background: Fine needle aspiration cytology (FNAC) is a widely used diagnostic tool to evaluate neoplastic or inflammatory tumorous lesions of the salivary glands. This method influences the selection of the modality of surgical treatment. In cases of benign tumors of the parotid gland, a (partial) superficial parotidectomy is usually recommended. However, for tumors other than pleomorphic adenomas (such as cystadenolymphomas, other adenomas, or benign tumor-like lesions) this operation is considered an overtreatment because extracapsular satellites are rare and recurrences in case of a capsular lesion are not likely. In such cases, a less extended surgery (enucleation) with lower morbidity is sufficient and can be carried out provided that pleomorphic adenomas and non-pleomorphic benign lesions are reliably differentiated prior to surgery. The aim of this study was to evaluate the reliability of the FNAC in differentiating benign tumors of the parotid gland.

Methods: A retrospective evaluation of 160 cases of benign parotid gland tumors was performed and the cytological diagnoses compared with the histomorphological results. A collection of 26 cases with false-negative and false-positive results was reevaluated.

Results: FNAC showed a sensitivity of 74.2% and a specificity of 89.8% for differentiation between pleomorphic adenomas and non-pleomorphic benign lesions. The predictive value for pleomorphic adenomas was 82.1%, and for non-pleomorphic benign lesions 84.6%. Reevaluation showed higher sensitivity (96.2%), specificity (98.9%), and negative/positive predictive values (97.9% and 98.1%, respectively).

Discussion/conclusion: Poor quality and hypocellularity of the cytological smears seem to negatively effect the outcome of the cytological diagnosis. It is concluded that only an accurate diagnosis of non-pleomorphic adenoma or a benign tumor-like lesion, based on an adequate FNAC specimen and assessed by an experienced cytopathologist, can justify tumor enucleation because the risk of pleomorphic adenoma is only 2% under these circumstances.