Risk of Malignancy in the Milan System for Reporting Salivary Gland Categories in Pediatric Population from Distinct...

The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) is applied widely in reporting salivary gland cytology in adult population; however, there are limited publications on its application in pediatric population and consequently on risk of malignancy (ROM) for each diagnostic category. The aim of this study was to evaluate the ROM for each diagnostic category in the MSRSGC in pediatric patients from different countries using only three published original studies.

FNA of the pediatric salivary gland lesions was assessed from three different studies: (1) Maleki et al., (2) Satturwar et al., and (3) Wang et al., and then classified based on the MSRSGC categories: nondiagnostic, non-neoplastic, atypia of undetermined significance (AUS), benign neoplasm, salivary gland neoplasm of uncertain malignant potential (SUMP), suspicious for malignancy (SM), and malignant. In each study, we reviewed the cases distributed according to the MSRSGC and recorded the ROM, as well as the available histological follow-up results.

The cases across the three different cohort studies showed different distributions using the MSRSGC category. The population of Maleki's cohort study had the highest total patients of around 477 cases. Also, it had the highest number of cases diagnosed as non-neoplastic (34.6%). On the other hand, the paper of Satturwar's series had around 32 cases that showed a predominance of benign neoplasms (34.4%). The third research paper by Wang's cohort had around 104 cases that demonstrated a higher proportion of malignant cases (5.8%) relative to total aspirates. The ROM values were also reviewed for each MSRSGC category and showed different outcomes between those three studies. The ROM of "SM" and "malignant" categories reached 100% in two cohort studies done by Satturwar's and Wang's series versus 60% and 90%, respectively, in Maleki's paper. Histologic follow-up was available for 49.7% of Maleki's, 65.6% of Satturwar's, and 51.9% of Wang's cases. The ROM for benign neoplasms was consistently low (<5-6%) across studies, while AUS and SUMP categories showed wide interstudy variability (AUS ROM: 20-100%; SUMP ROM: 31.8-67%).

This study of 613 salivary gland FNAs in pediatrics confirms that the MSRSGC is applicable on pediatric population with overall high reproducibility. The ROM was lower in benign neoplasm, while it was 100% in SM and malignant categories. Variations on ROM data are most likely due to sample size differences, and patient population and surgical follow-up.