A retrospective comparison of salivary gland fine needle aspiration reporting with the Milan system for reporting salivary gland cytology.

Abstract

Fine needle aspiration (FNA) is a routine sampling method in the diagnostic work up of salivary gland lesions. Despite universal use, no standardised classification existed for the cytopathological reporting of such entities until recently. The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) aims to standardise the reporting of these lesions, offering risk of malignancy rates and clinical management recommendations. We retrospectively applied MSRSGC to cases reported over a 5-year period. Salivary FNA specimens were reclassified according to the MSRSGC as (I) non-diagnostic, (II) non-neoplastic, (III) atypia of undetermined significance (AUS), (IV) benign neoplasm and salivary gland neoplasm of uncertain malignant potential, (V) suspicious for malignancy, and (VI) malignant. Cases with surgical resections were documented and risk of malignancy calculated for each group, where possible. We compared our outcomes with similar studies performed since publication of the Milan criteria. In total, 192 specimens were reassigned as non-diagnostic (n=30), non-neoplastic (n=31), AUS (n=1), benign neoplasm (n=97) and salivary gland neoplasm of uncertain malignant potential (n=4), suspicious for malignancy (n=3), and malignant (n=26). There were 73 surgical resections. Our calculated risk of malignancy was within the proposed MSRSGC rates for the non-diagnostic, benign neoplasm and malignant groups. One AUS case did not undergo surgery. Benign and malignant sensitivities and specificities for the original reporting categories were 88.24% and 95.72%, and 100% and 95.45% for the MSRSGC, respectively. Salivary gland FNA has high diagnostic accuracy and the MSRSGC offers standardised reporting and assistance in the stratification of cases. This may improve communication between pathologists and clinicians with improved outcomes for patients.