Anatomy of lymphatic drainage of the esophagus and lymph node metastasis of thoracic esophageal cancer

The lymphatic drainage of the inner layers (mucosa and submucosa) and the outer layers (muscularispropria and adventitia) of the thoracic esophagus is different. Longitudinal lymphatic vessels and long drainage territory in the submucosa and lamina propria should be the bases for bidirectional drainage and direct drainage to thoracic duct and extramural lymph nodes (LN). The submucosal vessels for direct extramural drainage are usually thick while lymphatic communication between the submucosa and intermuscular area is usually not clearly found, which does not facilitate transversal drainage to paraesophageal LN from submucosa. The right paratracheal lymphatic chain (PLC) is well developed while the left PLC is poorly developed. Direct drainage to the right recurrent laryngeal nerve LN and subcarinal LN from submucosa has been verified. Clinical data show that lymph node metastasis (LNM) is frequently present in the lower neck, upper mediastinum, and perigastric area, even for early-stage thoracic esophageal cancer (EC). The lymph node metastasis rate (LNMR) varies mainly according to the tumor location and depth of tumor invasion. However, there are some crucial LN for extramural relay which have a high LNMR, such as cervical paraesophageal LN, recurrent laryngeal nerve LN, subcarinal LN, LN along the left gastric artery, lesser curvature LN, and paracardial LN. Metastasis of thoracic paraesophageal LN seems to be a sign of more advanced EC. This review gives us a better understanding about the LNM and provides more information for treatments of thoracic EC.