Comparative cytological and histological assessment of 828 primary soft tissue and bone lesions, and proposal for a system for reporting soft tissue cytopathology

Introduction: The aim of the study was to evaluate the diagnostic utility of fine needle aspiration (FNA) cytology and core needle biopsies (CNBs) in a series of primary soft tissue and bone lesions and to test a possible system for reporting results of FNA cytology of soft tissue lesion. Methods: This retrospective study encompassed 828 primary soft tissue and bone lesions, analysed with FNA, CNB and/or surgical specimen in order to perform sensitivity/specificity as well as accuracy analyses. The series was then used to test a system for reporting soft tissue cytopathology with six categories and the risk of malignancy in each category was calculated. Results: With a malignant diagnosis defined as positive test result, FNA and CNB analysis showed sensitivity of 87% and 94%, respectively, and specificity of 89% and 95%, respectively. FNA and CNB analyses identified the correct histopathological entity of the examined lesion in 55% and 66%, respectively. The risk of malignancy within the tested categories was non-diagnostic 42%, non-neoplastic 0%, atypia of unknown significance 46%, neoplasm benign 3%, neoplasm of unknown malignant potential 27%, suspicious for malignancy 72% and malignant 97%. Conclusion: FNA cytology is a suitable tool to determine the malignant potential of a sampled soft tissue/bone lesion but is inferior to CNB in defining the correct entity. A standardised reporting system might improve the clinical management of patients with soft tissue tumours examined primarily by FNA cytology.