The Milan System at Memorial Sloan Kettering: Utility of the categorization system for in‐house salivary gland fine‐needle aspiration cytology at a comprehensive cancer center

Abstract

Background: The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) provides a standardized reporting system for salivary gland fine-needle aspiration (SGFNA). We review the clinical utility of the MSRSGC at a tertiary care cancer center by assessing the rates of malignancy (ROM) among different categories.Methods: A retrospective search was performed to retrieve all SGFNA cases performed at our institution between 1/1/07 and 12/31/18. The initial primary diagnoses were recorded and cases were then assigned to appropriate MSRSGC categories. ROM was then calculated for all categories.Results: A total of 976 cases were identified, and 373 with follow-up. The ROM was 19.7% (192/976) for all-comers and 51.3% (192/374) among cases with follow-up.Using MSRSGC, SGFNA showed a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 65.6%, 87.4%, 100%, and 72.6%, respectively. ROM for MSRSGC categories I, II, III, IVa, IVb, V, and VI were 20.7%, 30.0%, 45.8%, 3.3%, 50.7%, 100%, and 100%, respectively. Utilizing MSRSGC resulted in a nondiagnostic rate of 14.4%. The nondiagnostic rate was lower when the procedure was performed by pathologists vs nonpathologists (12.9% vs 15.8%) but was comparable when rapid on site evaluation (ROSE) was performed (12.9% vs 11.6%).Conclusion: In our patient population, MSRSGC resulted in a perfect PPV and moderate NPV. Utilizing MSRSGC results in a higher nondiagnostic rate due to the inclusion of cases with benign elements or cyst contents only in this category. Performing ROSE is more important in attaining an adequate sample than the specialty of the person performing SGFNA. K E Y W O R D Sfine-needle aspiration, Milan system for reporting salivary gland cytopathology, salivary gland

The Milan system for reporting salivary gland cytopathology: The clinical impact so far. Considerations from theory to practice

“…The non‐diagnostic category carries a risk of malignancy (ROM) of 25%. The publication of papers analysing the role of the Milan System has further defined the ROM . In a recent study by Tommola et al, the non‐diagnostic category had a 0% ROM; however, a recent meta‐analytic study by Farahani analysed 92 studies including 16,456 SG‐FNA with surgical follow‐up The data from this study revealed a 7% ROM for the non‐diagnostic category based on 44 cases with histological follow‐up.…”

“…The series also supported the statement that the non‐diagnostic rate should be <10%. Nevertheless, the rate of non‐diagnostic FNA in the studies conducted at general hospitals was 21.28% ± 17.47% as compared to 4.38% ± 2.32% performed at referral or tertiary centres demonstrating an advantage for the latter group . The most common clinical management is represented by a repeat FNA with the use of ultrasound guidance and/or rapid on‐site evaluation in order to prevent a second non‐diagnostic result .…”

“…The current commentary describes the diagnostic categories of the Milan System and the main features of them. Furthermore, we provide data from the most recent salivary series adopting the Milan System for reporting their salivary cases …”

“…Non‐neoplastic lesions of the SGs are common and include benign entities such as reactive, metaplastic and inflammatory changes associated with acute or chronic inflammation, structural alterations or infection . The implied ROM for the non‐neoplastic category is approximately 10%, with studies ranging from 0% to over 20% . The Milan System Atlas offers a detailed description of this category including diagnostic criteria, photomicrographs and tables of a wide variety of non‐neoplastic entities such as sialolithiasis, acute, chronic and granulomatous sialoadenitis .…”

“…The ROM for AUS is approximately 20%. According to a recent meta‐analysis, only 16 out of 92 studies used the term atypia for a total of 110 cases respecting the strict criteria suggested by the Milan System . Moreover, the data assessed that the prevalence of histological benign entities (including non‐neoplastic and benign neoplasms) was 63% with a ROM at around 37% The introduction of the AUS category will probably be useful for certain specific entities such as predominantly cystic and mucin‐rich low‐grade mucoepidermoid carcinoma.…”