Extent of Lymphadenectomy for Esophageal Cancer

Lymphatic Drainage of the Esophagus and Patterns of Spread

Knowledge of the lymphatic drainage of the esophagus is a key component for having a rationale for lymphadenectomy. The esophagus traverses three body compartments, and lymph flow can occur in a wide pattern of spread. The embryologic origin of the esophagus is from the branchial arches and pharyngeal pouches from above, and the splanchnic mesoderm below. These join during early embryologic development but remain demarcated at the level of the tracheal bifurcation leading to bilateral lymphatic drainage ( Fig. 40.1 ).

In early esophageal cancer the suggestion is that lymph node spread, when it occurs, follows these anatomic pathways, implying that the tumor location is key to determining which nodes are likely to be involved. Thus nodal involvement for tumors above the tracheal bifurcation is preferentially to those in the upper mediastinum and neck, whereas those below this point will metastasize toward the celiac axis. Tumors located at the bifurcation may metastasize in either direction. Skipping of lymph node stations in these early tumors is rare.

Lymph node involvement appears to be more common with squamous cell carcinoma (SCC) compared with adenocarcinoma when the tumor has invaded into the muscularis mucosae (T1a-M3), approaching up to 12%, compared with only 1.3% in adenocarcinoma.

There is also an extensive submucosal lymphatic network that allows longitudinal communication between the proximal and distal drainage systems. In tumors that are more advanced and have potentially led to a blockage of one of the primary pathways, this submucosal system allows eccentric lymph node involvement. This is an important consideration because most patients are diagnosed at a more advanced state and T3 disease is associated with an up to 85% chance of lymph node involvement.

Lymph Node Tiers

Extent of lymph node dissection is commonly divided into three fields: the upper abdomen, the mediastinum, and the neck ( Fig. 40.2 ). Three-field dissection therefore relates to removal of nodal tissue from each of these areas. A lack of clarity exists on the exact definition of a two-field lymph node resection. The lack of clarity is because of differences in prevalence of squamous cell cancer in Japan and the East and in those patients from Western countries where adenocarcinoma has become the prevalent cause.

Where SCC of the esophagus is the common pathology, a two-field dissection is usually described as removal of nodal tissue from the upper abdomen (around the celiac artery) and in the inferior and superior mediastinum and along both recurrent laryngeal nerves. To contrast this, in countries where adenocarcinoma has become the common variant, a two-field dissection is usually regarded as removal of tissue from the upper abdomen and inferior mediastinum. This usually extends only to the level of the carina and reflects the usual anatomic location of these tumors in the lower esophagus or at the esophagogastric junction.

Although some surgeons do not perform a formal lymphadenectomy irrespective of the surgical approach, the following describes what is commonly accepted to be the groups of nodes resected with each “field” of dissection.

Abdominal Lymph Node Dissection

This is commonly regarded as the first “field” of lymphadenectomy and includes the following abdominal lymph node stations: the superior gastric group, celiac trunk nodes, and common hepatic nodes (see Fig. 40.1 and Table 40.1 ).

The superior gastric nodes include those that are paracardial, which are frequently involved and are related to the most superior branch of the left gastric artery, and so both left and right paracardial should be considered a single group. The lesser curve nodes are involved with tumor spread to the celiac trunk and are also considered part of the superior gastric group, as are the nodes found along the length of the left gastric artery.

The celiac trunk nodes include those around the celiac axis at the root of the left gastric artery, common hepatic artery, and splenic artery, and they should be removed en bloc with the primary lesion. Disease beyond this drainage point represents metastatic disease. Similarly, disease involvement beyond the hepatic nodes equates to metastatic disease.

The involvement of nodes in both paracardial regions and lesser curve are the most commonly involved with tumors of the lower esophagus. Nodes close to the left gastric artery and celiac trunk and hepatic artery are also commonly involved, which is consistent with the lymphatic drainage of the proximal stomach and lower esophagus.

Intramural spread distally and hence involvement of these abdominal nodes, for patients with lower esophageal cancers, is greater with adenocarcinoma (54%) compared with SCCs (10%), indicating the need for a wide resection margin in these patients.