Intraoperative thoracoscopic view of the left upper mediastinum. A) An intraoperative view before the lymph node dissection of the left upper mediastinum. There was no aortic arch. The vagus nerve, which passed over the left subclavian artery, was identified. B) An intraoperative view after the upper mediastinal lymph node dissection. The recurrent laryngeal nerve, which branched from the vagus nerve, was identified. The recurrent laryngeal nerve passed beneath the arterial ligament. AL, arterial ligament; LSA, left subclavian artery; PA, pulmonary artery; PN, phrenic nerve; RLN, recurrent laryngeal nerve; VN, vagus nerve.