Fig. 52: Anatomic landmarks for defining N2 nodes in the lower tracheobronchial tree. The mediastinal nodes that lie along the right main bronchus and distal to the cephalic border of the azygos vein are classified N2. The area is depicted by "A" and the length of the right main bronchus is represented by "B". These distances are variable with the length of the main bronchus observed between 0 cm., with one or more segments of the upper lobe arising from the most distal trachea, to 2.5 cm. The length of the left main bronchus is less variable and the nodes along its length are classified N2.

Confirmation of N2 disease in patients who meet all other criteria of operability is recommended because all enlarged nodes do not contain metastatic disease and the positive predictive value of computed tomography for identification of positive mediastinal nodes is low^15-16. In the absence of proof, however, ipsilateral mediastinal lymph nodes greater than 1 cm. in diameter are staged N2¹⁷. Similarly, pre- and retrotracheal nodes that would be accessible to the surgeon at thoracotomy are classified N2.