Introduction of the WHO Reporting System for Lymph Node Cytopathology

Abstract

Lymph node fine needle aspiration biopsy (FNAB) is a useful diagnostic tool in the initial evaluation of lymphadenopathy of unknown etiology. The World Health Organization (WHO) Reporting System for lymph node cytopathology comprises five categories: Insufficient/Inadequate/Nondiagnostic, Benign, Atypical, Suspicious for Malignancy, and Malignant. This review focuses on the diagnostic criteria for each category, including cytomorphology, ancillary studies, differential diagnosis, and associated risk of malignancy. Its primary goal is to standardize the reporting and interpretation of lymph node samples, minimizing interobserver variability among pathologists. By establishing clear guidelines and standardized terminology, this system improves communication between pathologists and clinicians, leading to enhanced consistency, accuracy, and patient care in lymph node specimen evaluation. The WHO Reporting System serves as a unified and reproducible framework for the precise categorization of lymph node aspirates, enabling better communication between cytopathologists and clinicians and ultimately facilitating more effective patient management.