Cell Blocks and the Milan System for Reporting Salivary Gland Cytopathology: A Meta-Analysis

The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) is a classification system first released in 2018. It provides a standardized categorization for salivary gland lesions. Cell blocks can be prepared from fine-needle aspirations (FNAs) and can be utilized for the diagnostics of salivary gland lesions. This study aims to evaluate the distribution of the MSRSGC categories and the associated risks of malignancy (ROM) in salivary gland FNAs incorporating cell block preparations.

A PubMed literature search was conducted between March 3 and May 20, 2025, to identify studies with both cell block and MSRSGC applications in salivary gland FNAs. Data on sample size and the ROM for individual MSRSGC categories were extracted into Microsoft Excel and subsequently analyzed using OpenMetaAnalyst.

Five studies were identified with a total of 1132 FNA samples processed to cell blocks. The pooled distributions of samples in the present meta-analysis were 21.9% in non-diagnostic (ND), 6.4% in non-neoplastic (NN), 8.2% in atypia of undetermined significance (AUS), 30.0% in benign neoplasm (BN), 8.0% in salivary gland neoplasm of uncertain malignant potential (SUMP), 1.9% in suspicious for malignancy (SM), and 19.4% in malignant (MN). The pooled ROMs from this meta-analysis was 25.3% in ND, 16.5% in NN, 26.3% in AUS, 2.0% in BN, 28.7% in SUMP, 84.8% in SM, and 97.7% in MN.

The ROMs of the AUS and SUMP categories were lower than the compared meta-analyses. The cell block application utilizes architecture and ancillary studies, leading to better performance in indeterminate categories.