Rates of attainment of: the American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) criteria , which requires examination of a minimum of three N1 and three mediastinal nodes (a) or stations, including station 7 (b); and American College of Surgeons’ Oncology Group (ACOSOG) Z0030 systematic sampling criteria, which include examination of lymph nodes from stations 2R, 4R, 7 and 10R, for right-sided resections (c) and 4L,5,6,7 and 10L for left-sided resections (d). Horizontal bars indicate significant differences between intervention groups after Tukey adjustment for multiple comparisons (alpha=0.05).