Background: The use of fine needle aspiration biopsy (FNAB) for diagnosis of parotid gland masses (PGM) is questioned, because of low sensitivity and the generalized belief requiring surgery for most parotid masses. Information available is retrospective. Our objective was to evaluate the diagnostic accuracy of FNAB for diagnosis of patients with PGM.
Methods: A prospective diagnostic test study was conducted in a cancer center from 2003 to 2007. FNAB was obtained from patients older than 18 years with PGM. Cytopathologist and histopathologist were blinded for all clinical information. The reference standard for diagnosis was the surgical pathology report.
Results: FNAB sensitivity and specificity values in diagnosis of malignancy were 0.923 (95% confidence interval [CI], 0.85-0.99) and 0.986 (95% CI, 0.96-1.00), respectively. Positive and negative likelihood ratios (LRs) were 64.6 (95% CI, 9.22-453) and 0.078 (95% CI 0.03-0.18), respectively. Negative LR of FNAB was strengthened (0.078-0.029) when negative diagnosis of FNAB was associated with tumor size <4 cm, definite borders, and homogeneous tumor mass observed by computed tomography (CT).
Conclusion: Diagnostic accuracy for FNAB was very high. No clinical or radiological factors improved the positive LR of FNAB alone. Liberal use of FNAB of PGM is recommended.