LYMPH NODE MAP DEFINITIONS

N2 NODES - All N2 nodes lie within the mediastinal pleural envelope.

1. Highest mediastinal nodes: Nodes lying above a horizontal line at the upper rim of the bracheocephalic (left innominate) vein where it ascends to the left, crossing in front of the trachea at its midline.



2. Upper paratracheal nodes: Nodes lying above a horizontal line drawn tangential to the upper margin of the aortic arch and below the inferior boundary of #1 nodes.



3. Prevascular and retrotracheal nodes: Pre- and retrotracheal nodes may be designated 3A and 3P. Midline nodes are considered to be ipsilateral.



4. Lower paratracheal nodes: The lower paratracheal nodes on the right lie to the right of the midline of the trachea between a horizontal line drawn tangential to the upper margin of the aortic arch and a line extending across the right main bronchus at the upper margin of the upper lobe bronchus, and contained within the mediastinal pleural envelope; the lower paratracheal nodes on the left lie to the left of the midline of the trachea between a horizontal line drawn tangential to the upper margin of the aortic arch and a line extending across the left main bronchus at the level of the upper margin of the left upper lobe bronchus, medial to the ligamentum arteriosum and contained within the mediastinal pleural envelope.
   
   Researchers may wish to designate the lower paratracheal nodes as No. 4s (superior) and No.4i (inferior) subsets for study purposes; the No. 4s nodes may be defined by a horizontal line extending across the trachea and drawn tangential to the cephalic border of the azygos vein; the No. 4i nodes may be defined by the lower boundary of No. 4s and the lower boundary of No. 4, as described above.



5. Subaortic (A-P window): Subaortic nodes are lateral to the ligamentum arteriosum or the aorta or left pulmonary artery and proximal to the first branch of the left pulmonary artery, and lie within the mediastinal pleural envelope.



6. Para-aortic nodes (ascending aorta or phrenic): Nodes lying anterior and lateral to the ascending aorta and the aortic arch or the innominate artery, beneath a line tangential to the upper margin of the aortic arch.



7. Subcarinal nodes: Nodes lying caudal to the carina of the trachea, but not associated with the lower lobe bronchi or arteries within the lung.



8. Paraesophageal nodes (below carina): Nodes lying adjacent to the wall of the esophagus and to the right or left of the midline, excluding subcarinal nodes.



9. Pulmonary ligament nodes: Nodes lying within the pulmonary ligament, including those in the posterior wall and lower part of the inferior pulmonary vein.
   
   N1 NODES - All N1 nodes lie distal to the mediastinal pleural reflection and within the visceral pleura.



10. Hilar nodes: The proximal lobar nodes, distal to the mediastinal pleural reflection and the nodes adjacent to the bronchus intermedius on the right; radiographically, the hilar shadow may be created by enlargement of both hilar and interlobar nodes.



11. Interlobar nodes: Nodes lying between the lobar bronchi.



12. Lobar nodes: Nodes adjacent to the distal lobar bronchi.



13. Segmental nodes: Nodes adjacent to segmental bronchi.



14. Subsegmental nodes: Nodes around the subsegmental bronchi.