Comparison Study of FNAC Using the Milan System Cytopathology versus Definitive Histology for the Diagnosis of Salivary Gland Tumors

Introduction: Salivary gland tumors (SGT) represent 6 to 8 percent of head and neck tumors. The cytologic diagnosis of SGT is performed by fine-needle aspiration cytology (FNAC) with variable sensitivity and specificity. The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) categorizes the cytological results and provides the risk of malignancy (ROM). The aim of our study was to evaluate the cytological findings with the definitive pathological findings to assess the sensitivity, specificity, and diagnostic accuracy of FNAC in SGT according to MSRSGC classification. Method: An observational, retrospective, single-center study was carried out at a tertiary referral hospital over a period of 10 years. Patients that underwent FNAC for major SGT and that have undergone surgery to remove the tumor were included. A histopathological follow-up was performed on the surgically excised lesions. Results from the FNAC were categorized into one of the six MSRSGC categories. The sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy of FNAC for determining benign and malignant cases were calculated. Results: A total of 417 cases were analyzed. The cytological prediction of ROM was 10% in nondiagnostic, 12.12% in non-neoplastic, 3.58% in neoplasm benign group, 60% in AUS and SUMP groups, and 100% in suspicious and malignant group. The statistical analysis of sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy for determining benign cases was 99%, 55%, 94%, 93%, and 94%, respectively, and for determining malignant neoplasm was 54%, 99%, 93%, 94%, and 94%, respectively. Conclusion: In our hands, MSRSGC is highly sensitive for benign tumors and highly specific for malignant tumors. The low sensitivity to differentiate malignant from benign cases makes it necessary to apply an adequate anamnesis, physical examination, and imaging tests to consider surgical treatment in most cases.