Outlines: All recruited patients will undergo complete mediastinal lymphadenectomy. For tumors in the left lungs, removal of mediastinal nodal stations 5,6,7,8 and 9 are required. For tumors in the right lungs, removal of mediastinal nodal stations 2,4,7,8 and 9 are required. Frozen section histologic subtyping will be made intraoperatively. By the selective strategy, the patients with intraoperative AIS/MIA/LPA diagnosis will be considered as negative mediastinal metastasis and patients with an apical tumor will be considered as negative inferior mediastinal metastasis. Otherwise, the mediastinal nodal status will be determined by the post-operative pathology. The virtual staging results of this selective strategy will then be compared with the final staging results by the complete lymphadenectomy.