Milan Interobserver Reproducibility Study (MIRST): Milan System 2018.

•This is an image-based study performed in concert with the 2018 release of The Milan System for Reporting Salivary Gland Cytopathology monograph.•Survey aims included testing participants for ability to use The Milan System on included images and to identify cytomorphologic features and Milan reporting categories that might represent sources of poor interobserver agreement.•The most significant feature affecting the performance of survey responders in the application of The Milan System was the diagnostic category of the image.•Diagnostic categories with the best agreement were Neoplasm: Benign (58.9%), Non-Diagnostic (49.2%), and Malignant (48.4%) categories. Indeterminate categories including Atypia of Uncertain Significance (AUS) (17.7%) and Salivary Gland Lesion of Uncertain Malignant Potential (SUMP) (23.6%) showed lower concordance.•This study sets a reference point for future studies in interobserver reproducibility in salivary gland cytology, and a platform for determining the relative risk for diagnostic categories in The Milan System.