The Diagnostic Yield and Safety of Confocal Laser Endomicroscopy Assisted Endobronchial Ultrasound-guided Mediastinal Cryobiopsy Via a Tunnel for Diagnosing Mediastinal Lymphadenopathy: a Multi-center Randomized Controlled Trial.

Mediastinal and/or hilar lymphadenopathy (MHL) becoming more and more common in clinical practice with the development of imaging technique. MHL is secondary to various benign and malignant disorders that could be life-threatening conditions due to compression of airways or blood vessels. Accurate and timely diagnosis is important for managing patients with lymphadenopathy. Nowadays, several invasive mediastinal tissue samplings have been designed and development.

For patients with metastatic lymphadenopathy, endobronchial ultrasound (EBUS) guided transbronchial needle aspiration has been recommended as a first-line diagnostic method by several guidelines due to its highly diagnostic sensitivity for non-small cell lung cancer and acceptable safety.However, the relatively limited material retrieved by needle aspiration restricts its diagnostic yield in non-metastatic lymphadenopathy including sarcoidosis, lymphoma, tuberculosis, etc.6,7 It is important to obtain the representative sample which showed the specific pathology for diagnosing patients with non-metastatic lymphadenopathy. Therefore, previous studies attempt to use transbronchial mediastinal cryobiopsy (TBMC) to obtain acquiring samples with sufficient volume suitable for histological and molecular analyses.

Despite several studies have proved that TBMC has a highly diagnostic yield, the heterogeneity of pathologic characteristics in lymph node makes obtaining a representative sample difficult. To overcome the sampling heterogeneity and obtain the possibility of obtaining a representative sample in mediastinal lesions, increasing sampling number had been proved as an effective method in previous studies (5-times TBNA, thrice TBMC). With the increasing sampling number, the potential risk related to the procedure is higher than before.

Needle-based confocal laser endomicroscopy (nCLE) is a laser-based imaging technique that utilizes fluorescence for real-time microscopic imaging at the biopsy needle tip. Compared to EBUS, nCLE enables real-time visualisation of cell shapes, there by acting a real-time microscope. Besides, we had developed a novel procedure which can built a tunnel between airway wall and target lymph node using a puncture dilation catheter and allows various tools to perform procedure, its efficacy and safety had been proved in our published studies.Based on this tunnel, we could perform TBMC under the nCLE guidance. The area with representative pathology of lymph node may be detected by nCLE, and shorten the sampling number. However, it remains unknown which of these techniques is the superior match for needle biopsy.