Table 1. Mediastinal lymph node dissection and lymph node metastasis rate in each group.

N2 lymph node	n=256
Mean number of groups (groups)	4.1±1.3
Mean lymph node	12.3±6.9
Rate of lymph node metastasis
Group 2	18.18
Group 3	17.79
Group 4	30.83
Group 5	21.74
Group 6	17.79
Group 7	48.62
Group 8	4.74
Group 9	10.67