Prediction of Malignancy in Salivary Gland Tumors by a New Cytology Reporting System

Abstract

Objectives: The aim of this study was to analyze the risk of malignancy in salivary gland tumors on the basis of the Milan System for Reporting Salivary Gland Cytopathology. Methods: A retrospective review was performed of the charts of patients with salivary gland tumors in whom the final diagnosis was confirmed by surgical excision. Preoperative fine needle aspiration results were categorized according to the Milan System for Reporting Salivary Gland Cytopathology: non-diagnostic (category I), nonneoplastic (category II), atypia of undetermined significance (category III), neoplasm (category IV), suspicious for malignancy (category V), and malignant (category VI). Fine needle aspiration and final diagnosis were compared, and the risk of malignancy and operative/oncological outcomes were analyzed. Results: A total of 288 patients were enrolled in this study. Postoperative histopathologic salivary gland malignancies were found in 30 (10.4%) patients. Risk of malignancy was 7.1%, 0%, 48.0%, 4.8%, 88.7%, and 100% in categories I, II, III, IV, V, and VI, respectively. The most common malignant tumor in category III was salivary duct carcinoma (37.5%), followed by acinic cell carcinoma (25.0%), mucoepidermoid carcinoma (25.0%), and squamous cell carcinoma (12.5%). The 5-year survival rate of patients with malignant tumors showed no statistical difference between category III and category V/VI ( P = .140). Risk of malignancy was 88.9% and 100% in category V and VI, respectively. Conclusions: A half of atypia of undetermined significance (category III) cases were malignant. Once diagnosed, the prognosis of malignant tumor in category III was similar with that in category V/VI.