Reporting Bone Cytopathology-A Proposal Based on a Single Tertiary Centre Experience

Fine-needle aspiration cytology (FNAC) from bone lesions has been proven to be a useful diagnostic tool but lacks standardisation. The aim of the study was to evaluate the diagnostic utility of FNAC as a basis to propose and test a reporting system for bone reporting cytopathology. This retrospective study is based on patients with bone lesions, that were approached by cytology at Skåne University Hospital, Sweden between 2015 and 2023. The diagnostic performance was measured by sensitivity, specificity and accuracy analyses. All diagnoses were then distributed in six categories: (I) Non-diagnostic, (II) Benign, (III) Atypia, (IV) Bone neoplasm of uncertain significance, (V) Suspicious for malignancy and (VI) Malignant. The risk of malignancy (ROM) in each category was calculated. The final cohort consisted of 721 cases. Bone cytology was able to differentiate between benign and malignant lesion with a sensitivity of 89% and a specificity of 99%. The overall diagnostic accuracy was 65% but varied significantly among different types of lesions. Within the tested diagnostic categories, the ROM was (I) 48%, (II) 6.7%, (III) 69%, (IV) 28%, (V) 93% and (VI) 100%. FNAC from bone lesions is a sensitive and specific diagnostic tool with high diagnostic accuracy among various tumour types. This study provides valuable insights for the development of a standardised reporting system for bone cytopathology.