- All clinically suspicious mediastinal N1, N2, or N3 lymph nodes (> 1 cm short-axis dimension on CT scan and/or positive on PET scan) confirmed negative for involvement with NSCLC by one of the following methods: mediastinoscopy, anterior mediastinotomy, endoscopic and/or endobronchial ultrasonography (EUS/EBUS)-guided needle aspiration, CT-guided, or video-assisted thoracoscopic or open lymph node biopsy