Cytological specimens obtained by endobronchial ultrasound-guided transbronchial needle aspiration: Sample handling and role of rapid on-site evaluation

Recently developed, endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is a minimally invasive modality for mediastinal lymph node staging in lung cancer patients as well as for the diagnosis of mediastinal and hilar lymphadenopathy. It has been shown in systematic reviews and meta-analysis that a high diagnostic yield can be achieved with EBUS-TBNA for staging lung cancer. Though still not a standard of practice, this novel technology has attracted physicians and surgeons as an alternative modality to surgical biopsy for the assessment of the mediastinum. Standard cytology, thin layer preparations in liquid medium or cell blocks of cells obtained by EBUS-TBNA can be applicable not only for pathological diagnosis but also for further investigations such as immunohistochemistry and fluorescence in situ hybridization. In addition, samples obtained by EBUS-TBNA can also be used for molecular analysis. The key to a successful EBUS-TBNA is to understand the anatomy of the mediastinum as well as the basic steps of the procedure. Moreover, handling of the sample obtained by EBUS-TBNA is crucial for diagnosis since no amount of skill or interest of the interpreter can make up for a badly prepared sample. The goals of rapid on-site evaluation during EBUS-TBNA include determination of whether sampling of the target has been achieved and more importantly triage of samples to secondary investigations. This manuscript explains the detailed techniques of EBUS-TBNA to master this innovative procedure. Les cytoponctions transbronchiques échoguidées (EBUS-TBNA), récemment développées comme méthodes semi-invasives de la stadification ganglionnaire des cancers bronchiques, se sont rapidement étendues au diagnostic plus général des adénopathies médiastinales et hilaires. De nombreux articles et méta-analyses ont montré la haute rentabilité diagnostique de l’EBUS-TBNA dans la stadification des cancers bronchiques. Bien que ce ne soit pas encore une pratique de routine, cette nouvelle technologie est très attractive pour de nombreux pneumologues et chirurgiens comme méthode alternative aux biopsies chirurgicales dans l’exploration du médiastin. La cytologie standard, les prélèvements en milieu liquide ou les cytoblocs du matériel obtenu au cours des EBUS-TBNA s’appliquent, non seulement au diagnostic cytologique, mais également aux investigations complémentaires telles que l’immunocytochimie, ou l’hybridation in situ par fluorescence. De plus, les écha