Assessing the diagnostic accuracy for pleomorphic adenoma and Warthin tumor by employing the Milan System for Reporting Salivary Gland Cytopathology: An international, multi‐institutional study

Abstract

Background The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) has established distinct diagnostic categories for reporting cytopathological findings, and each is associated with a defined risk of malignancy (ROM). However, the ROM is applied at the overall category level and is not specific for particular morphological entities within a category. Here, the diagnostic performance of the MSRSGC for pleomorphic adenoma (PA) and Warthin tumor (WT) is reported. Methods The pathology archives of 11 institutions from 4 countries were retrospectively searched to identify all salivary gland fine‐needle aspiration (FNA) biopsies with a differential or definitive diagnosis of PA or WT and all resection specimens with a diagnosis of PA or WT; only paired cases were included. All FNA diagnoses were retrospectively classified according to the MSRSGC. Results A total of 1250 cases met the inclusion criteria, and they included 898 PA cases and 352 WT cases. The ROM in the benign neoplasm category was 3.0% and 1.3% for cases with a differential or definitive diagnosis of PA and WT, respectively. The ROM in the salivary gland neoplasm with uncertain malignant potential (SUMP) category was 2.7% and 18.8% for PA and WT, respectively (P = .0277). The diagnostic accuracy for PA and WT was 95.1% and 96.1%, respectively. Conclusions The diagnostic accuracy for PA and WT on FNA is high. Furthermore, these findings highlight the difference in the ROMs associated with 2 specific differential diagnoses in the SUMP category: basaloid neoplasms and oncocytoid neoplasms.

Assessing the diagnostic accuracy for pleomorphic adenoma and Warthin tumor by employing the Milan System for Reporting Salivary Gland Cytopathology: An international, multi‐institutional study

“…On a related note, we also found the authors' statement that “these findings highlight the difference in the ROMs associated with 2 specific differential diagnoses in the SUMP category: basaloid neoplasms and oncocytoid neoplasms” 1 to be perplexing. As the authors described, the selection criteria for their study specifically enriched for cases with cytologic features or a diagnosis of PA or WT 1 . Consequently, the data could not be extrapolated to represent ROMs associated with all aspiration samples classified as basaloid or oncocytoid SUMP.…”

“…Multi‐institutional collaborations such as that reported by Allison et al 1 are valuable resources for the cytopathology community. Such studies have the capacity to recruit a large and diverse study population, with the goal of generating data that have the potential to be more broadly applicable than those from single‐institution studies.…”

Reply to Assessing the diagnostic accuracy for pleomorphic adenoma and Warthin tumor by employing the Milan System for Reporting Salivary Gland Cytopathology: An international, multi‐institutional study

“…In our experience using MSRSGC, the next stage of development for this unique diagnostic system comes from possibly separating ROM calculations for cytologic diagnoses that can be made with a relatively high degree of confidence (eg, Warthin tumor and pleomorphic adenoma [PA]). The objective of our study 1 was to initiate that process and guide investigators in how data might be collected. Other data collection schemes may demonstrate usefulness.…”

“…To calculate ROM, the data are collected in such a way as to include the maximum number of each desired subject while surgical diagnosis remains the gold standard whenever cytology and/or histology correlation is required. If the aim of a study is to calculate the ROM for a diagnostic category such as the atypical category, the data can be retrieved in a “forward” fashion, similar to what we did in our previous studies 2‐7 or with a definitive diagnosis of PA and Warthin tumor as in our latest study 1 . However, if the goal of the study is to calculate the ROM for a diagnostic entity such as PA, the search then must be both forward and backward to include all desired cases.…”

Refining the Milan System for Reporting Salivary Gland Cytopathology

“…In this issue of Cancer Cytopathology , Allison and his colleagues use a large international and multi‐institutional cohort of salivary gland fine‐needle aspiration cases to investigate the diagnosis and reporting of pleomorphic adenomas and Warthin tumors in the MSRSGC 7 . Their work helps to clarify important cytological reporting aspects of these 2 common salivary gland tumors.…”