[OA-28] The Milan system for reporting salivary gland cytopathology: a 7-year retrospective institutional study

Sirawich Jessadapattarakol and Sasithorn Watcharadetwittaya

Department of Pathology, Facolty of Medicine, Khon Kaen University, Khon Kaen, Thailand

Fine needle aspiration (FNA) cytology is efficient in guiding salivary gland lesions management. Lack of standardised reporting complicates communication between pathologists and clinicians. The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) has been proposed to improve reporting uniformity. This study aimed to reclassify salivary gland FNA and evaluate risk of malignancy (ROM) in each diagnostic category. All salivary gland FNA cytology in Srinagarind Hospital from January 2013 to December 2019 were retrospectively reviewed and reclassified according to MSRSGC. The ROMs were calcolated using the available concurrent histology. A total of 699 cases were included and reclassified as non-diagnostic 333 (45.9%), non-neoplastic 145 (22.5%), AUS 28 (4.0%), benign 101 (14.5%), SUMP 42 (6.0%), suspicious for malignancy 39 (5.6%) and malignant 11 (1.6%). Histologic follow-up was available in 283 cases. The calcolated ROMs were 36.1% for non-diagnostic, 37.1% for non-neoplastic, 33.3% for AUS, 10.2% for benign, 50% for SUMP, 92% for suspicious for malignancy and 100% for malignant. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 42.9%, 98.0%, 93.1%, 72.9% and 76.5%, respectively. In conclusion, MSRSGC is a valuable classification system that establishes a standard reporting terminology and quantifies the risk of malignancy for each category.

Keywords: cytopathology; fine needle aspiration; risk of malignancy; salivary gland; Milan System