Background
Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) has a high diagnostic yield for the evaluation of mediastinal lesions. However, obtaining an adequate sample from necrotic lung or mediastinal lesions (NL) can be challenging. Tissue coagulum clot cellblock(TCC-CB) could increase the cellular yield of cell block (CB) but its? utility in NL remains less certain.

Method
Single-center retrospective analysis of EBUS-TBNA cases over 24 months to determine the utility of TCC-CB. Lesions demonstrating relative low attenuation (LA) on contrasted computed tomography were considered necrotic. EBUS-TBNA was performed using a 22G needle with 4 punctures per lesion. Samples were processed in cytology smear (CS), Cytolyt®fixation CB or TCC-CB. EBUS-TBNA was considered diagnostic if a definite cytological diagnosis was obtained.

Results
78 cases of EBUS-TBNA with 91 lesions targeted. Lesions comprised 64 (70.3%) lymph nodes (LN), and 27 (29.7%) lung or mediastinal masses. 26 lesions had (28.6%) LA compared to 65 non-LA (71.4%). The overall diagnostic yield from CS was 53.8% (42 patients), combined CS and CB was 71.8% (56 patients), and 78.2% (61 patients) with TCC-CB. Molecular analysis was successful in 73.3% (22/30 patients); TCC-CB was preferred over CB for analysis in 15 patients. Sub-analysis of 41 cases where samples were processed in three methods showed the overall diagnostic yield for LA lesions was 73.3% (11/15 patients). Diagnostic yield for LA lesions using TCC-CB versus combined CS and CB was 46.7% (7 patients) versus 26.7% (4 patients)(P=0.045) respectively.

Conclusion
TCC-CB is an option to increase the diagnostic yield of EBUS-TBNA, even in NL.