Comparison of Segmentectomy Versus Lobectomy for Lung Adenocarcinoma ≤ 2cm

Inclusion Criteria: * Tumor size ≤ 2 cm; * Solitary tumor and located in the outer third of the lung field; * Preoperative CT indicated that the nodules were single nodules or Concomitant nodules was less than minimal invasive adenocarcinoma; * Intraoperative frozen section confirmed invasive lung adenocarcinoma and with micropapillary and solid patterns positive (\>5%); * Confirmation of R0 status by intraoperative frozen section analysis; * Pulmonary function could withstand both segmentectomy and lobectomy (FEV1 \> 1.5 L or FEV1% ≥ 60%); * Sufficient organ function; * Performance status of 0,1 or 2； * Written informed consent. Exclusion Criteria: * The tumor is close to the hilum, which cannot perform segmentectomy ; * Patients suspected of lymph node positive by preoperative examination, including CT scans and mediastinal lymph node biopsy; * Evidence revealed locally advanced or metastatic disease; * Intraoperative exploration revealed accidental pleural dissemination. * Patients with severe damage to heart, liver and kidney function (grade 3 \~ 4, Alanine aminotransferase (ALT) and/or Aspartate aminotransferase (AST) over 3 times the normal upper limit, Cr over the normal upper limit). * Patients concomitant with other malignant tumors； * Patients had prior chemotherapy, radiotherapy or molecular targeted therapy for this malignancy. * History of severe heart disease, heart failure, myocardial infarction within the past 6 months. * The patients who were not suitable for inclusion by researchers' evaluation.