Receiver operating characteristic curves of the HAL model in the combined validation cohort. The figure plots the area under the curve (AUC) for A, N2 or N3 (vs N0 or N1) disease (AUC = 0.873) for all patients that met inclusion criteria from all 13 institutions (n = 1,799), and for B, N2 or N3 (vs N0 or N1) disease (AUC = 0.875) for patients that met inclusion criteria from institutions that had more than 50 eligible patients (n = 1,701). HAL = Help with the Assessment of Adenopathy in Lung cancer model.