Diagnostic Accuracy of Fine Needle Aspiration Cytology for High-Grade Salivary Gland Tumors

Background Preoperative differentiation between high-grade malignancy and others (benign or low-grade tumors) is more important than differentiation between malignant and benign tumors for surgical planning, treatment outcome, and prognosis in salivary gland tumors. Fine needle aspiration cytology (FNAC) has a relatively low sensitivity for differentiating malignant from benign salivary tumors. However, the diagnostic performance of FNAC has not been studied in predicting high-grade salivary malignancy, which can significantly affect patient care. Methods Experienced cytopathologists reevaluated the adequate FNAC on 521 salivary gland tumors. The diagnostic performances of FNAC for total malignancy and high-grade malignancy were calculated, and the results were validated in independent 105 cases. In cases of high-grade cancer on FNAC, we recorded the additional diagnostic procedures and the change of surgical extent to decide how FNAC impacts clinical practice. Results The sensitivity, specificity, and diagnostic accuracy of FNAC in differentiating malignant from benign tumors were 64.2 % (95 % confidence interval 52.3–75.0), 98.4 % (96.5–99.3), and 92.1 % (89.1–94.6). Meanwhile, FNAC predicted high-grade malignancy accurately (94.6 % [80.0–99.5], 99.2 % [97.8–99.7], 98.9 % [97.3–99.6], respectively), a finding reproduced with similar results in the validation set. FNAC indicative of high-grade malignancy added additional imaging assessments in 94.9 %, frozen biopsy samples during surgery (tumor and lymph nodes) in 71.2 %, and changed the extent of surgery in 59.0 %. Conclusions FNAC has an excellent diagnostic performance in discriminating high-grade salivary cancer, which guides clinical decision and surgical planning in salivary gland tumors.