Endobronchial ultrasound-guided transbronchial fine needle aspiration of mediastinal lymphadenopathy: Diagnostic performance and clinical implications of the World Health Organization reporting system.

Introduction: Lymph node fine-needle aspiration cytology (LN-FNAC) is a common, rapid, minimally invasive and cost-effective diagnostic method. For mediastinal lymph nodes, endobronchial ultrasound (EBUS) guided LN-FNAC is a first-line investigation and has an indispensable role in the diagnosis and staging of patients with suspected lung cancer. Recently, a new WHO system has been proposed for classification of LN-FNAC heralding five different diagnostic categories; insufficient, benign, atypical, suspicious for malignancy and malignant. The aim of this study was to evaluate the diagnostic accuracy and risk of malignancy (ROM) of these categories in EBUS-guided LN-FNAC from mediastinal lymph nodes.

Method: We evaluated 2110 consecutive mediastinal lymph nodes during this one-year retrospective study. Corresponding radiological images and histologic material were used as ground truth to calculate accuracy, sensitivity, specificity and ROM.

Results: The WHO system showed an overall accuracy of 93.7% with a sensitivity of 83.0% and a specificity of 97.5%. The positive predictive value was 92.3% and the negative predictive value 94.2%. The overall ROM for each category in the WHO classification system was 12.8% for the inadequate, 2.4% for the benign, 47.4% for the atypical, 81.0% for the suspicious for malignancy and 93.6% for the malignant category.

Conclusion: The results of the present study indicate that the new WHO system entails a high diagnostic accuracy regarding EBUS-guided LN-FNAC assessment of mediastinal lymph nodes and supports its integration into clinical practice. Application of the WHO system standardizes risk assessment thus facilitating communication between cytopathologists and clinicians and minimizes the need for histopathological analysis.