Risk of Malignancy Using the Diagnostic Categories Proposed by the World Health Organization International System for Reporting Pancreaticobiliary Cytopathology

Abstract

<b><i>Background:</i></b> The World Health Organization (WHO) proposed an updated reporting system for pancreaticobiliary cytology, which moves low-grade malignancies to “positive for malignancy” group and serous cystadenoma to “negative for malignancy” group. The WHO system also created two new categories, namely, pancreatic neoplasia-low grade (PaN-Low) and pancreatic neoplasia-high grade (PaN-High), which includes neoplastic mucinous cysts and stratifies them according to their cytologic atypia. The risk of malignancy (ROM) of the new categories of the WHO system needs to be defined. <b><i>Methods:</i></b> Cytologic slides of all patients, who underwent endoscopic ultrasound (EUS)-guided fine needle aspiration (FNA) biopsy at our institution from January 2010 to December 2021 and had a histopathological or clinical follow-up of at least 6 months, were reviewed and reclassified under the Papanicolaou Society of Cytopathology (PSC) and WHO reporting systems. The absolute ROM was calculated for each category of both reporting systems. <b><i>Results:</i></b> A total of 420 EUS-FNA samples from 410 patients were reviewed and reclassified. The absolute ROM for the proposed WHO system was 35% for “nondiagnostic,” 1.0% for “negative for malignancy,” 69.0% for “atypical,” 11% for “PaN-Low,” 100% for “PaN-High,” 91% for “suspicious for malignancy,” and 100% for “malignant.” Comparatively, the absolute ROM under the PSC reporting system was 34% for “nondiagnostic,” 1.0% for negative (for malignancy), 50.0% for “atypical,” 0.0% for “neoplastic: benign,” 16% for “neoplastic: other,” 88% for “suspicious for malignancy,” and 100% for “positive or malignant.” <b><i>Conclusion:</i></b> The proposed WHO international reporting system has advantages regarding risk stratification improvement and case management.

The World Health Organization classification of pancreaticobiliary cytopathology stratifies risk of malignancy and outcome for endoscopic ultrasound‐guided fine‐needle aspiration of the pancreas

“…We have compiled the largest cohort comparing the ROM and testing characteristics of the PSC and WHO systems for pancreatic EUS- The WHO classification is newly introduced, and thus far the reported AROM for the WHO classification is as follows: 7.7%-35%, 1.0%, 28%-69%, 4.8%-11%, 60%-100%, 91%-100%, and 100% for the WHO I, II, III, IV, V, VI, and VII categories, respectively. 7,8 For the PSC classification, the range of the AROM for studies with comparable methods to this study is 8%-57%, 1%-40%, 28%-100%, 0%, 0%-34%, 82%-100%, and 97%-100% for the PSC I, II, III, IVa, IVb, V, and VI categories, respectively. 3,4,6,[9][10][11][12] The ranges in AROM are likely due to heterogeneity in the proportions of cystic and solid lesions in the study cohorts.…”

“…The WHO classification is newly introduced, and thus far the reported AROM for the WHO classification is as follows: 7.7%–35%, 1.0%, 28%–69%, 4.8%–11%, 60%–100%, 91%–100%, and 100% for the WHO I, II, III, IV, V, VI, and VII categories, respectively 7,8 . For the PSC classification, the range of the AROM for studies with comparable methods to this study is 8%–57%, 1%–40%, 28%–100%, 0%, 0%–34%, 82%–100%, and 97%–100% for the PSC I, II, III, IVa, IVb, V, and VI categories, respectively 3,4,6,9–12 .…”

“…As a result, we observed a higher AROM for categories I, II, and III. 7,8 Our subanalysis of cystic lesions yielded an AROM within the range of two studies of the PSC classification limited to cysts: 17%-33%, 0%-11%, 29%, 19%-21%, 80%-100%, and 100% for the PSC I, II, III, IV, V, and VI categories, respectively. 5,13 The data presented herein agree with recent reports that supported the validity of the WHO system's separation of low-and highgrade pancreatic neoplasms.…”

“…Similar studies have reported 25%-41% histologic correlation and a median clinical follow-up of 18-58 months. 3,8 The percentage of cases with results for cfCEA or molecular testing was lower than expected, and comparison with the AROMs for a cohort having these tests performed more consistently would be interesting. The study setting in a cancer center may limit the ability to generalize the data to all practice settings.…”

“…For example, sensitivity and specificity for the diagnosis of malignancy have been reported as 92.7% and 96.5%, respectively. 8 For pancreatic cysts, pooled specificity and sensitivity of EUS-FNA are 89% and 77%, respectively. In a prospective multi-institutional study, sensitivity was 46% (0.36-0.56) and specificity was 97% (0.92-0.99).…”