Prevalence and echo features of mediastinal lymph nodes in EUS for non-malignant indications: a prospective study in a Southern European Population

Background and study aims  Significant heterogeneity in geographic distribution regarding the prevalence of mediastinal lymph nodes (MLN) has been documented in autopsy and computed tomography (CT) studies. Awareness of the local prevalence and characteristics of lymph nodes will be relevant when performing endoscopic ultrasonography (EUS) for staging of malignant neoplasias. The aims of this study were to document the prevalence and echo features of MLN in patients undergoing EUS for non-malignant extrathoracic disease and to identify predictive factors for the presence of MLN. Patients and methods  A prospective single-center study was performed over 6 months. Mediastinal stations 9, 8, 7, 6, 5, 4 L and 2 were systematically evaluated using a linear echoendoscope in all patients undergoing EUS due to benign extrathoracic pathology and without history of oncologic disease. Demographic, clinical and EUS features of the lymph nodes were analysed. Results  Seventy-five patients were included: male/female 32/43; mean age, 63 years. The majority of patients (72 %) had lymph nodes in at least one mediastinal station and 88 % of these were found in stations 7 or 4 L. Overall, 133 MLN were identified: 19 % were hypoechogenic, 6 % had a short-axis diameter > 10 mm, and 6 % were round. The prevalence of lymph nodes was higher in smokers (83 % vs 64 %, P  = 0.024), with a higher average number of lymph nodes per patient in this group (2.1 vs 1.6; P  = 0.017). By logistic regression analysis, none of the variables analyzed were independently associated with the presence of MLN. Conclusion  This prospective Portuguese study documented a higher prevalence of MLN than previously reported in Northern Europe, in patients with no evidence of oncologic disease. This higher prevalence may negatively influence the specificity and positive predictive value for malignancy of MLN (N) staging by EUS.