Diagnostic Accuracy of Fine-Needle Aspiration Cytology in Salivary Gland Tumors: A 1331-Patient Multicenter Analysis of Institutional Variability and Size-Dependent Pitfalls

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Introduction: Fine-needle aspiration cytology (FNAC) is a standard preoperative diagnostic tool for salivary gland tumors, yet its sensitivity is widely debated. Aim: This study evaluates the diagnostic accuracy of FNAC compared to final histopathology, with a specific focus on institutional variability and the influence of tumor size on diagnostic yield. Methods: A retrospective, multicenter analysis was conducted on 1331 patients who underwent surgical resection for salivary gland tumors across five tertiary centers. After excluding incomplete records, 1031 patients with informative FNAC results were analyzed. Diagnostic performance (sensitivity, specificity, accuracy, and likelihood ratios) was calculated by comparing preoperative cytology with final histopathology. Statistical evaluations (Chi-square, Welch's t-test) assessed the impact of patient demographics, tumor dimensions (4 cm), and institutional location on diagnostic concordance. Results: The overall diagnostic accuracy of FNAC was 94.1%. The procedure demonstrated excellent specificity (98.4%) but suboptimal sensitivity (50.0%), confirming a high false-negative rate. Significant institutional variability was observed (p < 0.001), with local sensitivities ranging from 16.7% to 69.2%. Tumor size significantly impacted diagnostic accuracy (p = 0.0258), peaking in intermediate lesions (2-4 cm; 95.0%) but declining in both smaller (<2 cm; 93.7%) and larger neoplasms (>4 cm; 91.9%). An independent review of 298 initially non-diagnostic aspirates revealed a substantial subset of histologically confirmed malignancies, demonstrating that non-informative cytological smears cannot be assumed benign. Conclusions: While FNAC provides highly specific evidence for salivary gland malignancies, its low sensitivity and susceptibility to institutional and size-dependent variables limit its reliability in ruling out cancer. High false-negative rates, particularly in tumors exceeding 4 cm, necessitate a multimodal diagnostic approach. Integrating core needle biopsy for challenging lesions and intraoperative frozen section analysis is crucial to mitigate cytopathological limitations and ensure appropriate surgical management. .