Milan System for Reporting Salivary Gland Cytopathology- An overview with Interobserver Variability and Clinicoradiological Concordance

Introduction: Salivary gland lesions are one of the most heterogenous lesions with overlapping features between low grade malignancy and benign lesions thus making them one of the most difficult areas for diagnosing. Cytology of salivary gland lesions plays an extremely important part in diagnosing the lesions and categorising them into non neoplastic, benign and malignant neoplasms, thereby allowing the patients and clinicians to make an accurate decision regarding whether the lesion is followed, biopsied, excised or a radical operation might be needed. Aim: To classify salivary gland lesions according to MILAN System for Reporting Salivary Gland Cytopathology (MSRSGC). Materials and Methods: This observational study was conducted from June 2021 to May 2022 where Fine Neddle Aspiration Cytology (FNAC) of salivary gland lumps was done on patients presenting to the Department of Pathology Rohilkhand Medical College and Hospital, Bareilly. The clinical and radiological features were noted. The cases were diagnosed on conventional cytopathology. Additionally categorisation as per MILAN System was done by two pathologists independently. The results were compared with histopathology, where available. Data was collected, entered and compiled in Microsoft excel followed by analysis using the software Statistical Package for Social Sciences (SPSS) version 23.0. The data was represented in frequency and further analysed using Kappa statistics. Also the validity was calculated in terms of sensitivity, specificity, Positive Predictive Value and Negative Predictive Value (NPV). Results: Total of 60 cases were included with M:F ratio as 1.6:1. Most common age group was third decade with 17 (28.3%) cases, closely followed by fourth decade with 11 (18.3%) cases. Most common salivary gland to be affected was parotid gland with 30 (50%) cases. Most common MILAN category was II, non neoplastic with 26 (43.3%) cases, followed by IV A, benign neoplasm with 19 (31.67%) cases. The Cohen kappa coefficient was 0.952 which showed a near perfect agreement between the two pathologists. The sensitivity, specificity, PPV and NPV and accuracy was 75%, 92.8%, 75% and 92.8%, 89% respectively. The Risk of Malignancy (ROM) for category I,II,III,IVA,VI was 0%, 0%, 50%, 9%, 100% respectively. Conclusion: The MILAN System for Reporting Salivary Gland Cytopathology (MSRSGC) offers a structured reporting system. The terminologies are reproducible and convey clear meaning among all the medical professionals including different pathologists and treating physician or surgeon and guide in deciding the accurate treatment based on the ROM for different categories.