Level of carina of trachea

The carina of the trachea (tracheal bifurcation) is an anatomic landmark in the IASLC lymph node map, serving as a key boundary between several lymph node stations:

• The carina marks the upper boundary of Station 7 (subcarinal nodes), which extends inferiorly from the carina down to the level of origin of the left lower lobe bronchus and right middle lobe bronchus.

• The carina also serves as a landmark distinguishing superior mediastinal stations (above the carina) from inferior mediastinal stations (at and below the carina). Stations 1 to 4 (paratracheal nodes) lie above the carina, while Station 7 begins at the carina.

• On the right side, the lower border of Station 4R is defined by the lower border of the azygos vein, which lies near the level of the carina. On the left side, Station 4L extends from the top of the aortic arch to the upper border of the left pulmonary artery, with the carina approximating this transition zone.