The World Health Organization Reporting System for Pancreaticobiliary Cytopathology

Area of Science:

• Cytopathology
• Oncology
• Gastroenterology

Background:

• Standardized reporting is crucial for accurate pancreaticobiliary cytopathology diagnosis.
• Previous systems, like the Papanicolaou Society of Cytopathology (PSC) system, had limitations in classifying neoplastic lesions.
• The World Health Organization (WHO) Classification of Tumours series provides a foundation for standardized reporting across various body sites.

Purpose of the Study:

• To introduce and detail the new WHO Reporting System for Pancreaticobiliary Cytopathology.
• To revise and improve upon the existing PSC system for pancreaticobiliary cytology reporting.
• To provide an evidence-based terminology with risk of malignancy and management recommendations.

Main Methods:

• Development of a seven-tiered reporting system, replacing the previous six-tiered PSC system.
• Reclassification of neoplastic lesions, distinguishing between benign, premalignant, and low-grade malignant neoplasms.
• Emphasis on correlation with imaging and incorporation of ancillary testing (biochemical, molecular).

Main Results:

• The new WHO system features seven tiers: insufficient/inadequate/nondiagnostic; benign; atypical; low risk/low grade neoplasm; high risk/high grade neoplasm; suspicious for malignancy; and malignant.
• Key differences from the PSC system include the placement of low-grade malignancies (PanNETs, SPNs) into the 'malignant' category.
• Premalignant ductal lesions are now primarily categorized under 'neoplasm' based on cytomorphological grade.

Conclusions:

• The WHO Reporting System for Pancreaticobiliary Cytopathology offers a refined, evidence-based approach to diagnosis.
• The revised classification of neoplasms improves risk stratification and guides patient management.
• The system accommodates variations in ancillary testing availability, particularly in resource-limited settings.