Application of the WHO reporting system for soft tissue cytopathology with assessment of risk of malignancy: a retrospective study

Soft tissue tumors are complex neoplasms requiring accurate diagnosis, often through fine needle aspiration (FNA). The World Health Organization (WHO) classification system aims to standardize cytopathological diagnoses and assess the risk of malignancy (ROM) for these tumors.

This retrospective study reviewed cytological specimens from January 2022 to June 2023. Samples were categorized using the WHO classification into 6 categories: nondiagnostic, benign, atypical, soft tissue neoplasm of uncertain malignant potential, suspicious for malignancy (SFM), and malignant. Histopathological correlation was performed, and ROM, sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were calculated.

A total of 203 samples were analyzed: 62.5% benign, 13.8% SFM, and 9.9% malignant. ROMs were 33.3% (nondiagnostic), 1.2% (benign), 40% (atypical), 25% (soft tissue neoplasm of uncertain malignant potential), 80% (SFM), and 100% (malignant). Histopathological correlation was available for 117 cases. Sensitivity and diagnostic accuracy were highest (77.3% and 93.9%) when SFM and malignant categories were combined as positive for malignancy. Specificity was highest (100%) when only malignant cases were considered positive. The interobserver agreement was moderate (Cohen's kappa 0.45).

The WHO classification system for soft tissue cytopathology improves diagnostic accuracy and standardizes reporting. It effectively categorizes soft tissue tumors and guides clinical management, though further refinement is needed for broader applicability.