Reproducibility assessment of WHO reporting system for pancreaticobiliary cytopathology: A single institution experience.

Background: The World Health Organization (WHO) reporting system for pancreaticobiliary cytopathology was released to internationalize the reporting, assisting in correct diagnosis and patient treatment with significant revisions from the previous Papanicolaou Society of Cytopathology (PSC) system. The "neoplastic: benign" and "neoplastic: other" categories have mostly been superseded by two new ones: "pancreatic neoplasia-low-grade" (PaN-low) and "pancreatic neoplasia-high-grade" (PaN-high), which classify intermediate neoplastic lesions based on cytological atypia. We aim to assess the reproducibility and risk of malignancy (ROM) for reporting pancreaticobiliary cytopathology by the WHO system in comparison with the PSC system.

Materials and methods: A retrospective study by reviewing archival slides sent for pancreaticobiliary cytological evaluation from June 2021 to June 2023, by two pathologists blinded to each other's findings. Absolute ROM was determined by histopathology/cell block study/clinical follow-up (minimum 6 months)/overtly malignant imaging/metastasis.

Results: A total of 332 cases from 329 patients met the inclusion criteria, comprising pancreatic, gallbladder, and biliary lesions. The median patient age was 54 years (range, 14-86 years). The overall sensitivity of the test is 74.9% specificity is 93.2%, positive predictive value of 96.8%, negative predictive value of 57.6%, and a diagnostic accuracy of 81.8%. The absolute ROM for each site in all categories was comparable with that of the published data from the WHO system.

Conclusion: Our study highlights the reliability of the WHO system for guiding clinical decision-making and patient management in the context of pancreaticobiliary. However, continual efforts among pathologists are essential to maintain consistent accuracy in cytological interpretations.