Application of the WHO Reporting System for Soft Tissue Cytopathology in Bone and Soft Tissue FNAs : Diagnostic Accuracy and Risk of Malignancy Analysis

INTRODUCTION: Recently, a standardized reporting system for soft tissue cytopathology was introduced. The aim is to evaluate the diagnostic utility of FNA in the diagnosis of bone and soft tissue lesions by comparing the cytological and histopathological diagnoses in a large group of cases and to determine the risk of malignancy (ROM) rates according to the World Health Organization (WHO) Reporting System for Soft Tissue Cytopathology. MATERIALS AND METHODS: The pathology databases were searched for cases that underwent FNA for bone and soft tissue lesions between 2020 and 2023. Only cases that had available histological follow-up were included. The FNAs are categorized as nondiagnostic (ND), benign, atypical, soft tissue neoplasm of uncertain malignant potential (STNUMP), suspicious for malignancy (SM), malignant (primary/metastatic) according to WHO Reporting System for Soft Tissue Cytopathology. The risk of malignancy (ROM) was calculated for each group. RESULTS: The study consisted of 427 cases, including 30 ND (7%), 322 benign (75.4%), 19 atypical (4.5%), 7 STNUMP (1.6%), 5 SM (1.2%), and 44 malignant (10.3%). The ROM rates were 16.6%, 1.8%, 57.9%, 28.5%, 80%, and 100% for the groups: ND, benign, atypical, STNUMP, SM, and malignant, respectively. The diagnostic accuracy, sensitivity, and specificity of FNA in all bone and soft tissue lesions were 98.6%, 92.3%, and 100%, respectively. CONCLUSION: We conclude that FNA is a simple and accurate technique for assessment of bone and soft tissue lesions. The WHO Soft Tissue Cytopathology Reporting System could improve communication among pathologists and clinicians, simplify clinical management of patients, and support further research in soft tissue cytology.