Nondiagnostic salivary gland FNAs are associated with decreased risk of malignancy compared with 'all-comer' patients: Analysis of the Milan System for Reporting Salivary Gland Cytopathology with a focus on Milan I: Nondiagnostic

摘要

BACKGROUND: The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) reports a 25 rate of malignancy (ROM) for the Milan I: Nondiagnostic (ND) category. We clarify the ROM of ND salivary gland fine-needle aspirations (SGFNAs) based on our institutional experience and review of the literature. METHODS: Overall risk of malignancy (OROM) and that for those with surgical/flow cytometric follow-up (FROM) for each category and "all-comers" were calculated for Emory SGFNAs from January 2010 through March 2021. From a literature review of 50 articles using MSRSGC, distribution of diagnoses, rates of follow-up, FROM, and OROM by category were calculated. FROMs and OROMs between ND FNAs and all-comers were compared. Milan I rate was compared with the ratio of Milan I OROM to all-comer OROM. RESULTS: Of 819 SGFNAs at Emory, 12.8 (n = 105/819) were ND. Thirty-two had known follow-up, with 12 (37.5) being malignant. Nonmucinous cyst contents accounted for 26.7 of ND SGFNAs (n = 28/105); all 7 with surgical follow-up were benign. Of 50 MSRSGC studies, 18.2 (n = 2384/13,129) of SGFNAs were classified as ND, 26.6 (n = 635/2384) with known follow-up. Total FROM and OROM for ND FNAs (15.7 and 4.1, respectively) were significantly lower than those for all-comers (24.9 and 11.4, respectively) (p<.001). There was no relationship between rate of ND SGFNA and ND ROM. CONCLUSIONS: The ND category is associated with a lower ROM than that of all-comer SGFNA patients. The "true" ROM for ND SGFNAs is likely best estimated by the 4.1 OROM. SGFNAs showing nonmucinous cyst contents have a particularly low ROM. Rate of ND SGFNAs does not influence ND ROM.