Thoracic endosonography (EBUS/EUS-b) in the diagnosis of different intrathoracic diseases: A 4-year experience at a single-centre in Greece

Expression of PD-1/PD-L1 axis in mediastinal lymph nodes and lung tissue of human and experimental lung fibrosis indicates a potential therapeutic target for idiopathic pulmonary fibrosis

BACKGROUND

Mediastinal lymph node enlargement is prevalent in patients with idiopathic pulmonary fibrosis (IPF). Studies investigating whether this phenomenon reflects specific immunologic activation are lacking.

METHODS

Programmed cell death-1 (PD-1)/ programmed cell death ligand-1 (PD-L1) expression in mediastinal lymph nodes and lung tissues was analyzed. PD-1, PD-L1 mRNA expression was measured in tracheobronchial lymph nodes of mice following bleomycin-induced injury on day 14. Finally, the effect of the PD-1 inhibitor, pembrolizumab, in bleomycin-induced pulmonary fibrosis was investigated.

RESULTS

We analyzed mediastinal lymph nodes of thirty-three patients (n = 33, IPF: n = 14, lung cancer: n = 10, concomitant IPF and lung cancer: n = 9) and lung tissues of two hundred nineteen patients (n = 219, IPF: 123, controls: 96). PD-1 expression was increased, while PD-L1 expression was decreased, in mediastinal lymph nodes of patients with IPF compared to lung cancer and in IPF lungs compared to control lungs. Tracheobronchial lymph nodes isolated on day 14 from bleomycin-treated mice exhibited increased size and higher PD-1, PD-L1 mRNA levels compared to saline-treated animals. Pembrolizumab blunted bleomycin-induced lung fibrosis, as indicated by reduction in Ashcroft score and improvement in respiratory mechanics.

CONCLUSIONS

Mediastinal lymph nodes of patients with IPF exhibit differential expression profiles than those of patients with lung cancer indicating distinct immune-mediated pathways regulating fibrogenesis and carcinogenesis. PD-1 expression in mediastinal lymph nodes is in line with lung tissue expression. Lower doses of pembrolizumab might exert antifibrotic effects. Clinical trials aiming to endotype patients based on mediastinal lymph node profiling and accordingly implement targeted therapies such as PD-1 inhibitors are greatly anticipated.

Interventional Pulmonology and Esophagus: Combined Endobronchial Ultrasound and Endoscopic Ultrasound for Mediastinal Staging

Endoscopic ultrasound (EUS) techniques in addition to endobronchial ultrasound (EBUS) can lead to diagnosis and complete accurate staging of the mediastinum in a single session. This allows for decreased health care costs, less delay in diagnosis and treatment, reduced patient discomfort, and decreased morbidity compared with invasive surgical staging techniques. In comparison to conventional mediastinoscopy, the cost-effectiveness and reduced complication profile of the endoscopic approach has made this a superior initial step in the staging and diagnosis of lung cancer. Moreover, compared with EBUS alone, combined EUS and EBUS has significantly increased yield, as well as diagnostic sensitivity making a combined approach preferable as the emerging gold-standard technique for initial minimally invasive mediastinal staging. We discuss the advantage of using EUS in combination with EBUS and highlight techniques, lymph node landmarks, utility in staging and restaging of the mediastinum, roles in diagnosing mediastinal infections and granulomatous lesions, and future directions in endosonography.