Background: Fine needle aspiration (FNA) cytology has been widely used in the preoperative evaluation of salivary gland lesions. The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) is a tiered risk-stratification scheme designed to standardize reporting and facilitate decision making. We aimed to clarify the validity and diagnostic utility of the MSRSGC-based classification of salivary gland lesions.Methods: A total of 1020 salivary gland FNA specimens were retrieved between 2008 and 2017, with histologic follow-up data available for 349 specimens. Within the present retrospective study, each specimen with follow-up data was reclassified according to the MSRSGC diagnostic categories: nondiagnostic, nonneoplastic, atypia of undetermined significance (AUS), benign neoplasm, salivary gland neoplasm of uncertain malignant potential (SUMP), suspicious for malignancy (SM), and malignant.The risk of malignancy (ROM) was calculated based on the histologic follow-up data.
Results: The diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of the MSRSGC-based classification of the malignant potential of salivary gland lesions were 80.1%, 70.4%, 99.2%, 90.5%, and 96.7%, respectively. The ROM calculated for specimens assigned to the nondiagnostic, nonneoplastic, AUS, benign neoplasm, SUMP, SM, and malignant categories were 8.6%, 15.4%, 36.8%, 2.6%, 32.3%, 71.4%, and 100%, respectively. Conclusion: The present results confirm the validity and diagnostic utility of MSRSGC, supporting its use in clinical practice to help devise adequate management strategies for salivary gland lesions. K E Y W O R D S cytopathology, Milan System, MSRSGC, salivary gland 1 | INTRODUCTION In the management of salivary gland lesions, fine needle aspiration (FNA) cytology represents a cost-effective and minimally invasive procedure. It has been widely applied to differentiate nonneoplastic from neoplastic lesions, which is useful in the development of management strategies, ranging from conservative observation to complete surgical excision, and it can also provide prognostic information. 1 However, interpretation of the FNA of salivary gland lesions still poses a great challenge for pathologists and cytopathologists because of the relatively low cellularity in the cystic lesion, morphological heterogeneity within the tumor, and obvious overlapping morphologic features between benign and low-grade malignant tumors. For example, the lack of specific cytologic architecture to evaluate tumor invasion makes it difficult to distinguish between basal cell adenoma and basal cell adenocarcinoma, as the cytomorphology of the two neoplasms are similar. 2-5 The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) is a standardized reporting system designed to
