Application of the Milan System for Reporting Salivary Gland Cytopathology: A Retrospective 12-Year Bi-institutional Study

Abstract

Objectives: Multi-institutional studies are required for the validation of the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC).

Methods: A total of 1,560 fine-needle aspirations of the salivary glands were retrieved from two institutions for a 12-year period. The diagnoses were reclassified based on the MSRSGC. Risk of malignancy (ROM) for each category was calculated based on 694 histologic follow-up cases.

Results: The ROM for each category was: 18.3% for nondiagnostic, 8.9% for nonneoplastic, 37.5% for atypia of undetermined significance (AUS), 2.9% for benign neoplasm, 40.7% for salivary gland neoplasm of uncertain malignant potential (SUMP), 100% for suspicious for malignancy, and 98.3% for malignant. The sensitivity, specificity, positive predictive rate, and negative predictive rates were 89%, 99%, 98%, and 96%, respectively.

Conclusions: The results of the current study are in keeping with the MSRSGC. The indeterminate categories of AUS and SUMP showed intermediate ROMs at 37.5% and 40.7%, respectively.

Keywords: Cytology; Fine needle aspiration (FNA); Milan System for Reporting Salivary Gland Cytopathology (MSRSGC); Risk of malignancy (ROM); Salivary gland.