Application of Milan System for Reporting Salivary Gland Cytopathology: A 7 Year Study

Abstract

Introduction: Salivary gland shows various pathological conditions ranging from cystic, inflammatory, tumor like and neoplastic lesions. Fine needle aspiration cytology (FNAC) plays an important role in evaluating salivary gland (SG) tumors. Salivary gland tumors are one of the most heterogeneous groups of neoplasms with cytopathological features overlapping among the entities and making it difficult to assign to specific category. Due to these facts, salivary gland cytopathology is one of the most challenging areas of cytology. The lack of a uniform reported guidelines in salivary gland cytopathology leads to inter-observer variability and disagreements. The present study was undertaken to assess the degree of inter-observer reproducibility for diagnostic categorization of salivary gland lesions utilizing MSRSGC among pathologists with varying experience along with its role in providing a framework for reporting salivary gland lesions. Materials and Methods: In this cross sectional study, total of 44 cases of salivary gland lesions subjected to FNAC over a period of 7 year were studied. The cases were critically reviewed by 2 pathologists and a pathology resident with variable experience in cytopathology using MSRSGC in our institution. Inter-observer variability was assessed by comparing the agreement between two cytopathologists and pathology resident by using Cohen’s kappa statistics (Io score) and interpretation of the results was done using scale of Landis and Koch. Results: All the salivary gland aspirates were categorized according to MSRSGC.Out of 44 cases, maximum cases 22 (50%) were classified under IVA (BN) followed by 27.27% to 29.5% cases classified under II (NN), 2.27-4.55% of cases under Category IVB (SUMP), 4.55% under category V( SM) and 6.82% cases under category VI ( M). Inter-observer variability (IOV) was calculated for individual category in Milan system using Cohens kappa test, which was found to be in the almost perfect agreement range as per Landis and Koch, for categories II, IVA, V, VI ( Io score 0.89- 1). Kappa score ranged from 0.645 - 1 for category I (ND), which showed substantial to an almost perfect agreement. Whereas, category IVB (SUMP) showed variable results, with substantial agreement (Io score 0.656) to no agreement (Io score 0) between different observers.The overall IOV showed an almost perfect agreement with a kappa score of 0.861(obs1 vs 2) ,0.896 (obs1 vs R), 0.965 (obs 2 vs R). The data was found to be statistically significant (p=< .0001). Conclusion: MSRSGC is a very efficient system and has the potential to standardize salivary gland FNA diagnoses, providing clear prognostic and management information to clinicians and surgeons. This system can be used with good reproducibility between observers with variable cytopathology experience. Placing lesions in categories using MSRSGC can result in optimal management of discordant cases without using a specific diagnosis. Application of MSRSGC has immense value for standardization of reporting of salivary gland FNAC.Hence we recommend the use of Milan system for reporting salivary gland cytopathology.