MEDIASTINAL LYMPH NODES

The mediastinal lymph nodes are now classified into regional lymph node stations for the purposes of staging lung cancer. Involvement of these lymph nodes by cancer cells has important prognostic implications and influences the choice of treatment (Mountain & Dresler 1997). The staging system for lung cancer classifies involvement of hilar lymph nodes as N1, mediastinal lymph nodes as N2 and supraclavicular or scalene nodes as N3. Nodes that are contralateral to the tumour site are also classed as N3 nodes. The mediastinal nodes (N2 nodes) consist of all lymph node stations within the mediastinal pleural reflections.
Station 1: highest mediastinal nodes lie above a horizontal line of the level at which the left brachiocephalic vein crosses the trachea.
Station 2: upper para-tracheal nodes lie below the line of the highest mediastinal nodes and above a line drawn horizontally at the level of the upper border of the aortic arch.
Station 3: prevascular and retro-tracheal nodes lie behind the trachea but in front of the great vessels.
Station 4: lower para-tracheal nodes lie below the upper margin of the aortic arch and down to the upper margin of the corresponding upper lobe bronchus. On the right side, this is the upper margin of the right upper lobe bronchus; the majority of nodes in this area tend to be positioned anterolateral to the trachea. On the left side, the nodes are located below the upper margin of the aortic arch and above the margin of the left upper lobe bronchus. They lie medial to the ligamentum arteriosum and are usually lateral to the trachea.
Station 5: subaortic nodes lie in the aortopulmonary window and are situated lateral to the ligamentum arteriosum or aorta or left pulmonary artery, but proximal to the first division of the left pulmonary artery.
Station 6: para-aortic nodes lie between the upper margin of the aortic arch and lateral to the ascending aorta and aortic arch.
Station 7: subcarinal nodes lie below the carina of the trachea, but are not associated with the lower lobe bronchi.
Station 8: para-oesophageal nodes lie at either side of the oesophagus, well below the level of the subcarinal nodes.
Station 9: pulmonary ligament nodes lie within the pulmonary ligament.
The lymph nodes of the trachea, bronchi and lungs.
 
    Figure 59.24 The lymph nodes of the trachea, bronchi and lungs. Note the large 'carinal' node lodged between the bifurcation of the principal bronchi.
These groups are not sharply demarcated. Pulmonary nodes become continuous with the bronchopulmonary nodes, and they in turn merge with the inferior and superior tracheobronchial nodes, which are continuous with the para-tracheal group. Afferents of tracheobronchial nodes drain the lungs and bronchi, thoracic trachea, heart and some efferents of the posterior mediastinal nodes. Their efferent vessels ascend on the trachea to unite with efferents of the para-sternal and brachiocephalic nodes as the right and left bronchomediastinal trunks. The right trunk may occasionally join a right lymphatic duct or another right-sided lymph trunk and on the left the thoracic duct; however, more often they open independently in or near the ipsilateral jugulo-subclavian junction.


UPDATE Date Added: 14 August 2006

Abstract: Anatomy of right recurrent nerve node: why does early metastasis of esophageal cancer occur in it?
Click on the following link to view the abstract: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16718401&query_hl=31&itool=pubmed_docsum Anatomy of right recurrent nerve node: why does early metastasis of esophageal cancer occur in it? Mizutani M, Murakami G, Nawata SI, et al: Surg Radiol Anat 2006.