Comparison of endobronchial ultrasound-guided transbronchial needle aspiration cytology versus cell blocks in adults with undiagnosed mediastinal lymphadenopathy

Introduction: Retrospective studies have shown improved diagnostic yield of combined cytology and cell blocks specimens from endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) with variable additional yields in cell blocks. In this prospective study, we assessed the diagnostic performance of cytology and cell blocks in patients undergoing EBUS-TBNA.

Methods: This was a single-center, cross-sectional study conducted between December 2017 and November 2019 including patients aged ≥18 years with mediastinal lymphadenopathy. EBUS-TBNA was performed under conscious sedation using 22G needles. Both cytology smears and cell blocks by the tissue coagulum clot technique were prepared for each patient without rapid on-site evaluation.

Results: Data were analyzed for 93 patients (mean age 54.25 ± 13.7 years, 73 males) where both cytology and cell blocks were available. Sample adequacy was 100%. Overall diagnostic yield either by cytology or cell block was 83%. Cytology yield was 79.6%, whereas cell block was diagnostic in 73% of patients (P < 0.001). The overall additional yield of cell blocks was 3.2%. Cell blocks had additional yields of 1.8%, 0%, and 14.3% in malignancy, tuberculosis, and sarcoidosis, respectively. Tumor histology was better identified in 76% of positive cell blocks, and accurate histological subtyping was possible in 32.6% cases. Immunohistochemistry was feasible in 82.5% of all positive cell blocks, and these were judged to be adequate for the mutational analysis.

Conclusions: Compared to cytology, EBUS-TBNA cell blocks did not significantly increase the overall diagnostic yield in unselected patients. However, cell blocks are beneficial in the characterization of tumor morphology and histological subtyping of lung cancer.