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.

Application of the Milan System for Reporting Salivary Gland Cytopathology: A retrospective study in a tertiary institute

“…The ROM rates for the other categories were broadly in line with those suggested in the MSRSGC. Overall, the ROM rates obtained in our institution were within previously reported ranges for all diagnostic categories (Table ) …”

“…In the studies of Rossi et al, Viswanathan et al, and Wu et al, lymphoma was the main cause of false negative results with classification in the nonneoplastic category, whereas Rohilla et al reported that the ROM of the nonneoplastic category was ascribed to mammary analog secretory carcinoma, mucoepidermoid carcinoma, and carcinoma ex pleomorphic adenoma. In our study, the six specimens in the benign neoplasm category were found to be carcinoma ex pleomorphic adenoma (n = 5) or MALT lymphoma (n = 1) at the surgical follow‐up, which is similar to the observations of Viswasnathan et al and Wu et al, who found that most false negative cases in the benign neoplasm category were carcinoma ex pleomorphic adenoma (8/16). Rohilla et al reported three cases of false negative diagnoses in the benign neoplasm category, including mucoepidermoid carcinoma (n = 2) and oncocytic carcinoma (n = 1), while in the study by Rossi et al, there were 28 false negative diagnoses in which mucoepidermoid carcinoma (7/28, 25%) comprised the majority of the results.…”

“…Rohilla et al reported three cases of false negative diagnoses in the benign neoplasm category, including mucoepidermoid carcinoma (n = 2) and oncocytic carcinoma (n = 1), while in the study by Rossi et al, there were 28 false negative diagnoses in which mucoepidermoid carcinoma (7/28, 25%) comprised the majority of the results. Upon combining the results of the nonneoplastic and benign neoplasm categories, the false negative rate in the current study was 3.3%, which is close to the value reported by Wu et al (4.1%), but lower than the values reported in other studies, which ranged roughly from 5% to 15% . The most common false negative diagnoses in the nonneoplastic and benign neoplasm categories were lymphoma, carcinoma ex pleomorphic adenoma, and mucoepidermoid carcinoma.…”

“…Previous studies showed different false negative results in the nonneoplastic categories. In the studies of Rossi et al, Viswanathan et al, and Wu et al, lymphoma was the main cause of false negative results with classification in the nonneoplastic category, whereas Rohilla et al reported that the ROM of the nonneoplastic category was ascribed to mammary analog secretory carcinoma, mucoepidermoid carcinoma, and carcinoma ex pleomorphic adenoma. In our study, the six specimens in the benign neoplasm category were found to be carcinoma ex pleomorphic adenoma (n = 5) or MALT lymphoma (n = 1) at the surgical follow‐up, which is similar to the observations of Viswasnathan et al and Wu et al, who found that most false negative cases in the benign neoplasm category were carcinoma ex pleomorphic adenoma (8/16).…”

“…Lymphoma is a potential diagnostic pitfall in the nonneoplastic category. Without the assistance of immunophenotyping studies, low‐grade lymphoma could be misinterpreted as reactive lymphoid hyperplasia . In our study, specimens with a pathologic diagnosis of carcinoma ex pleomorphic adenoma had been diagnosed as pleomorphic adenoma on the original FNA cytology, which likely indicates a sampling error.…”