Beyond the adult standard: Tailoring the WHO Reporting System for Lymph Node Cytopathology to pediatric diagnostics...

The World Health Organization (WHO) Reporting System for Lymph Node, Spleen, and Thymus Cytopathology (WHO System) offers a standardized five-category framework to enhance diagnostic consistency. Although globally applicable, its risk of malignancy (ROM) and management protocols are largely generalized. This study explores the system's specific applicability and clinical utility within the pediatric population.

The study presents a pediatric diagnostic pathway centered on fine-needle aspiration biopsy, implemented according to the protocols established by the WHO System. The methodology emphasizes the integration of a multidisciplinary approach. The five WHO categories are evaluated through the lens of pediatric-specific differential diagnoses.

In pediatric practice, the Benign category often includes exuberant immunoblastic proliferation (e.g., Epstein-Barr virus) that mimics malignancy. Atypical and Suspicious categories represent a critical "gray zone" where the ROM is significantly influenced by the rarity of malignancy. Findings suggest that for Suspicious and Malignant categories, the use of rapid on-site evaluation (ROSE) under optimal conditions allows for an immediate transition to ancillary testing and clinical staging.

Pediatric application requires shifted interpretive thresholds. Monotonous small cell populations, which might suggest low-grade B-cell lymphoma in adults, typically represent reactive processes or aggressive small round blue cell tumors in children. The interventional pathologist is vital in reducing "non-diagnostic" rates. Furthermore, a "malignant" or "suspicious" diagnosis should trigger immediate multidisciplinary intervention to prevent complications.

The WHO System is a robust tool for pediatric evaluation when contextualized within pediatric-specific biological parameters. Integrating ROSE and interventional pathology minimizes invasive procedures and accelerates time-to-treatment for life-threatening malignancies.