Last-intercalated node and direct lymphatic drainage into the thoracic duct from the thoracoabdominal viscera.

Abstract

We clarified the configuration of the mediastinal lymphatics, focusing on the last intercalated lymph node and the direct drainage vessel to the thoracic duct, based on recent anatomical findings. We macroscopically observed the lymphatics during dissections of 205 cadavers in combination with routine histology. We also review the results of injection by other researchers. Efferent vessels draining directly into the thoracic duct or venous angle were frequently found in the following node groups: the right paratracheal node group corresponding to the last intercalated node in 98% of cadavers (201); the brachiocephalic angle node group in 85% of cadavers (174); the right recurrent nerve group in 46% (94); the left superior phrenic node group in 73% (150); the node group at the origin of the left common carotid artery (the preaortico-carotid node) in 37% (76); the pretracheal node group in 25% (51) and the left tracheobronchial node group in 36% (74). Last intercalated nodes appeared common for multiple drainage routes or regional lymphatics. These results were mostly consistent with injection studies by Riquet et al. Direct lymphatic drainage from the esophagus to the thoracic duct was observed in 19% of cadavers (39). Direct lymphatic drainage of lung segments to distant mediastinal nodes is also reviewed. The sentinel node concept is discussed in relation to the above observations. We hypothesize that the most critical sentinel node, if such usage is allowed, is situated as a guard for a limited specific route and for a common drainage route. We term it the "common terminal node".