Systematic review and meta-analysis of the diagnostic accuracy of the World Health Organization reporting system for soft tissue cytopathology.

[INTRODUCTION] The WHO recently proposed a standardized reporting system for soft tissue cytopathology to enhance diagnostic consistency, malignancy risk stratification, and communication between clinicians and pathologists. This 6-tiered system-nondiagnostic, benign, atypical, soft tissue neoplasm of uncertain malignant potential (STNUMP), suspicious for malignancy, and malignant-assigns estimated risks of malignancy to each category. Its diagnostic performance in soft tissue fine-needle aspiration (FNA) has not yet been comprehensively evaluated.

[MATERIALS AND METHODS] We conducted a systematic review and meta-analysis to assess the diagnostic performance of the WHO system in soft tissue FNAs. PubMed and EMBASE were searched through April 30, 2025. Included studies evaluated FNAs of soft tissue lesions with histopathology/clinicoradiologic follow-up as reference. Diagnostic performance was assessed at 3 thresholds: (1) "Malignant", (2) "Suspicious for malignancy" and above, and (3) "STNUMP" and above. Pooled sensitivity, specificity, area under the curve (AUC), and diagnostic odds ratios were calculated using a random-effects model.

[RESULTS] Four studies met inclusion criteria. ROMs ranged from 4% ("Benign") to 98% ("Malignant.") Sensitivity and specificity were 59% and 99% (AUC: 77%) for the "Malignant"-only threshold. Including "Suspicious" improved sensitivity to 75% (specificity: 98%, AUC: 84%). The broadest threshold yielded 85% sensitivity and 94% specificity (AUC: 82%). DORs ranged from 84.99 to 289.02. "Nondiagnostic" cases had a 33% ROM.

[CONCLUSIONS] The WHO system shows robust diagnostic accuracy for soft tissue FNA. Optimal performance occurs when "Suspicious" and higher categories are treated as positive. High ROM in nondiagnostic cases highlights the need for adequate sampling.