The utility of the Milan System as a risk stratification tool for salivary gland fine needle aspiration cytology specimens

Objective To perform a retrospective investigation of our institutional experience with salivary gland fine needle aspirations ( FNA ) through the framework of The Milan System for Reporting Salivary Gland Cytopathology ( MSRSGC ) and assess the risks of neoplasm and malignancy for each diagnostic category. Methods All salivary gland FNA s performed from January 2009 to December 2016 were retrospectively categorised according to the MSRSGC . When available, pre‐operative cytological results were correlated with subsequent histological follow‐up. Results In total, 893 FNA s were reviewed. The specimens were retrospectively classified as nondiagnostic ( ND : 13.5%), non‐neoplastic ( NN : 16.1%), atypia of undetermined significance ( AUS : 10.8%), benign neoplasm ( BN : 34.9%), salivary gland neoplasm of uncertain malignant potential ( SUMP : 8.2%), suspicious for malignancy ( SM : 2.7%) and malignant (M: 13.8%). Histological follow‐up was available for 429 cases (48%); the majority (68.1%) were benign. The risks of neoplasm and malignancy for each category were as follows: ND : 64.5%, 16.1%; NN : 42.9%, 17.9%; AUS : 79.6%, 30.6%; BN : 100%, 2.2%; SUMP : 100%, 46.6%; SM : 94.7%, 78.9%; and M: 100%, 98.5%. Conclusions The MSRSGC is a useful classification scheme for stratifying salivary gland lesions according to their associated risk of malignancy and guiding clinicians toward appropriate management. Diagnostic pitfalls are seen in a small proportion of cases and a multidisciplinary approach for assessing salivary gland pathology is essential in their evaluation.