Salivary Gland Cytopathology – The Milan System for Reporting Salivary Gland Cytopathology and diagnostic approach

The diagnosis of salivary gland tumors is considered difficult because of the variety of histopathological types, overlapping histological features (e.g., basaloid, cribriform, and oncocytic cells) in several tumor types, and the presence of low-grade carcinomas with less atypia. Fine-needle aspiration cytology (FNAC) is useful for the preoperative diagnosis of salivary gland lesions. However, there have been many differences in sensitivity and specificity among cytopathologists and institutions, and it has been pointed out that it does not always contribute to the determination of treatment strategies. In response, the Milan System for Reporting Salivary Gland Cytopathology (MSRGC), an international common reporting format, was developed and is now a global standard. The MSRGC consists of six diagnostic categories of cellular assessment, each with an evidence-based risk of malignancy (ROM), to contribute to recommended clinical management. In addition, cellular findings specimens that are considered inadequate are specifically described as non-diagnostic. The categories of 'atypia of undetermined significance' and 'salivary gland neoplasm of uncertain malignant potential' are defined separately to clarify the management of gray zone lesions and to emphasize the importance of identifying neoplastic disease for surgical treatment. It is hoped that MSRGC will be widely used in the pre-operative diagnosis of salivary gland lesions.