Pattern of lymph node metastases of squamous cell esophageal cancer based on the anatomical lymphatic drainage system: efficacy of lymph node dissection according to tumor location.

Knowing the anatomical lymphatic drainage of the esophagus is crucial to understanding the dissemination pattern of esophageal tumor. During the embryonal growth, the middle and lower part of the esophagus stretches as the lymphatic networks develop in the submucosal layer. The abundant submucosal lymphatics drain in a longitudinal fashion directly to their proximal and distal ends. The lymphatic route from the proximal esophagus through recurrent nerve nodes to supraclavicular nodes are a component of the mesentery of the proximal esophagus. The lower esophagus mostly drains its lymph into paracardial nodes related to celiac nodes through the mesentery of the distal esophagus. Lymphatic routes to mid and lower paraesophageal nodes usually originate from the intermuscular area of the muscularis propria. The lymphatic communication between the submucosa and intermuscular area is limited. The anatomical concept was confirmed clinically by a large series of single institution and the nationwide registry in Japan. The clinical data for the incidence of involved nodes verified the anatomical observations that long longitudinal extension of lymphatic drainage in the submucosa connected to the upper mediastinum lymphatics and paracardial lymphatics. The extent of dissection should be not tailored according to the anatomical distance from the tumor but according to the incidences of metastasis of each area, those were differed by tumor location. The areas for node dissection should be modified according to the tumor location. Although in patients with tumor limited to within the submucosal layer, even with tumors located in the mid- and lower esophagus, lymphatic metastasis was frequent in the upper mediastinum and perigastric area via the abundant submucosal lymphatics in a longitudinal fashion. When tumor invades or penetrates the muscle layer, the incidence of paraesophageal lymph node metastasis in the middle and lower mediastinum increases.