Thoracic lymph node stations

Professor Giovacchino Pedicelli and Dr Tim Luijkx ◉ ◈ et al.

Thoracic lymph nodes are divided into 14 stations as defined by the International Association for the Study of Lung Cancer (IASLC) ¹, principally in the context of oncologic staging. For the purpose of prognostication, the stations may be grouped into 7 zones. The IASLC definitions leave some ambiguous regions which can lead to misclassification ³.

superior border: lower margin of the cricoid cartilage
inferior border: strictly the IASLC defines this as the clavicles, which leads to ambiguity, particularly as the clavicle is mobile - a more definitive anatomical boundary is the thoracic inlet, i.e. 1st rib ²
left (1L) and right (1R) are divided by the mid-line of the trachea
station 1 nodes are outside the mediastinum and staged as an N3 disease; despite this, they can sometimes be treated with radical intent if they are encompassable in a radiotherapy field

Upper zone (superior mediastinal nodes)

Station 2 (left/right): upper paratracheal nodes

superior border: apex of lung / pleural space, thoracic inlet ²
left (2L) and right (2R) are divided along the left lateral border of the trachea, not the midline
inferior border of 2R: at the intersection of caudal margin of the left brachiocephalic vein with the trachea, i.e. abuts 4R
inferior border of 2L: superior border of the aortic arch, i.e. abuts 4L

Station 3A & 3P: pre-vascular and retrotracheal nodes

superior border: thoracic inlet
inferior border: carina
3A: prevascular - anterior to the great vessels (superior vena cava on the right, left common carotid artery on the left), posterior to the sternum
3P: retrotracheal - posterior to the trachea

Station 4 (left/right): lower paratracheal nodes

left (4L) and right (4R) are divided along the left lateral border of the trachea, not the mid-line
4R:
- superior border: intersection of caudal margin of the left brachiocephalic vein with the trachea, i.e. abuts 2R
- inferior border: inferior border of the azygos vein
4L:
- superior border: superior border of the aortic arch, i.e. abuts 2L
- inferior border: superior border of the left main pulmonary artery

pre-carinal nodes
- lymph nodes anterior to the tracheal bifurcation are inferior to the above anatomic definitions and are thus technically unclassified by IASLC
- these nodes are in the mediastinum (N2) and their surgical management mirrors that of 4R/4L lymph nodes, hence, pre-carinal nodes are best classified as part of the 4R/4L stations ²

Aortopulmonary zone

Station 5: subaortic nodes (aortopulmonary window)

lateral to ligamentum arteriosum
superior border: inferior border of the aortic arch
inferior border: superior border of the left main pulmonary artery

Station 6: para-aortic nodes, ascending aorta or phrenic

anterior and lateral to the ascending aorta and aortic arch
superior border: line tangential to the upper border of the aortic arch
inferior border: lower border of the aortic arch

Subcarinal zone

Station 7: subcarinal nodes

superior border: carina
inferior border - left: upper border of the lower lobe bronchus
inferior border - right: lower border of bronchus intermedius

Lower zone (inferior mediastinal nodes)

Station 8 (left/right): para-esophageal nodes (below carina)

superior border: station 7, i.e. upper border of lower lobe bronchus on left, and lower border of bronchus intermedius on right
inferior border: diaphragm

Station 9 (left/right): pulmonary ligament nodes

lying within the pulmonary ligament
superior border: inferior pulmonary vein
inferior border: diaphragm

Hilar and interlobar zone (pulmonary nodes)

Station 10 (left/right): hilar nodes

immediately adjacent to mainstem bronchus and hilar vessels
superior border: lower border of the azygos vein on the right, the upper border of the pulmonary artery on the left