The Milan System SUMP Category: 5-Year Diagnostic Performance

Abstract

Background: Salivary gland neoplasms are heterogeneous, with wide cytomorphological overlap. Neoplasms categorized in the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) as salivary gland neoplasms of uncertain malignant potential (SUMP) reflect this diagnostic challenge. Methods: All salivary gland fine-needle aspirations (SG-FNA) diagnosed at Fimlab Laboratories over a 5-year period (January 1, 2018–December 31, 2022) that were classified as SUMP were included. Follow-ups were reviewed until May 31, 2024. The SUMP cases were classified into cytomorphological subtypes. The risk of malignancy (ROM), risk of neoplasm, and median timelines of the pathology laboratory workflow and patient management were calculated. In addition, separate analyses of the impact of age and sex were performed. Results: A total of 1157 SG-FNAs were diagnosed over a 5-year period. Of these, 100 SG-FNAs from 52 females and 33 males were classified as SUMP. A total of 69 (69.0%) SUMP cases underwent histological verification. The ROM was 23.2% for all surgical follow-ups, 35.0% for the oncocytic/oncocytoid subtype, and 18.4% for the basaloid subtype. For the male and female groups, the ROMs were 26.9% and 16.2% for all surgical follow-ups, 40.0% and 14.3% for the oncocytic/oncocytoid subtype, and 18.8% and 16.7% for the basaloid subtype, respectively. Conclusions: The 5-year analysis of SUMP category performance showed a lower ROM in our practice than the MSRSGC reference value. The oncocytic/oncocytoid subtype presented a higher ROM than the basaloid subtype. The ROMs were highest in the male population and in the age group of 30–69 years.