Risk of malignancy and overall survival associated with the diagnostic categories in the World Health Organization Reporting System for Pancreaticobiliary Cytopathology.

BACKGROUND

The World Health Organization (WHO) classification system revised the Papanicolaou Society of Cytopathology (PSC) system for reporting pancreaticobiliary cytopathology. To better stratify intraductal and/or cystic neoplasms by cytologic grade, the neoplastic, other category was replaced by two new categories: pancreaticobiliary neoplasm, low-risk/grade (PaN-Low) and pancreaticobiliary neoplasm, high-risk/grade (PaN-High). Low-grade malignancies were placed in the malignant category, and benign neoplasms were placed in the benign/negative for malignancy category.

METHODS

An institutional pathology database search identified patients who underwent endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) for pancreatic lesions from January 2015 to April 2022. The absolute risk of malignancy (ROM) was determined by histologic and/or clinical follow-up of at least 6 months, and overall survival rates were calculated across diagnostic categories, comparing the WHO and PSC systems.

RESULTS

In total, 1012 cases were reviewed and recategorized. The ROM for the WHO system was 8.3% for insufficient/inadequate/nondiagnostic, 3.2% for benign/negative for malignancy, 24.6% for atypical, 9.1% for PaN-Low, 46.7% for PaN-High, 75% for suspicious for malignancy, and 100% for malignant. Comparatively, the ROM for the PSC system was 7.4% for nondiagnostic, 3.0% for negative for malignancy, 23.1% for atypical, 0% for neoplastic, benign, 7.3% for neoplastic, other, 75% for suspicious for malignancy, and 100% for malignant. The WHO system demonstrated superior stratification for overall survival.

CONCLUSIONS

The WHO system significantly improves the stratification of ROM and overall survival across diagnostic categories by introducing the PaN-Low and PaN-High categories and reassigning low-grade malignancies to the malignant category. Analyzing EUS-FNA samples with the WHO system provides critical insights for guiding clinical management.