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 seven zones. The IASLC definitions leave some ambiguous regions which can lead to misclassification 3.
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Supraclavicular zone
Station 1 (left/right): low cervical, supraclavicular, and sternal notch nodes
- 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 midline 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 and 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 midline
- 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
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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
Station 11: interlobar nodes
- between the origin of the lobar bronchi
Peripheral zone (pulmonary nodes)
Station 12: lobar nodes
- adjacent to lobar bronchi
Station 13: segmental nodes
- adjacent to segmental bronchi
Station 14: subsegmental nodes
- adjacent to subsegmental bronchi
- subsegmental