Topographical anatomy of the internal mammary lymphatics in the superior mediastinum and anterior mediastinal lymph nodes.

The lymphatics lying along the internal thoracic artery and vein, which are termed the "internal mammary lymphatics" (IML), were minutely dissected in 134 adult cadavers (80 males and 54 females, aged 27-94 years) in order to clarify the configuration of IML in the superior mediastinum. On the right side, IML frequently terminated at the brachiocephalic angle (BA) nodes and often at the nodes situated at an intermediate position between the internal thoracic artery and vein. By way of these nodes, IML communicated with regional lymphatics of the lung and esophagus. Moreover, IML joined the right superficial bronchomediastinal trunks. On the left side, IML consistently terminated at a superficial group of aortic arch nodes, termed the "superior phrenic nodes", lying along the left phrenic nerve and lying medially to the internal thoracic vein and inferiorly to the left brachiocephalic vein. At and around these nodes, IML joined drainage routes from the so-called Botallo's nodes, which received the left lung lymphatics. The efferents of the superior phrenic nodes formed the left superior bronchomediastinal trunks, and passed deeply to the left brachiocephalic vein and on the subclavian artery toward the left venous angle region. Consequently, IML formed common drainage routes with the drainage routes from the lung and esophagus in the superior mediastinum. A transverse communicating route of IMLs via the retromanubrial nodes, lying inferior to or along the left brachiocephalic vein, was often observed. On the right side, the communicating route terminated at the BA nodes or the nodes situated at an intermediate position between the internal thoracic artery and vein. On the left side, the route consistently terminated at the superior phrenic nodes. In addition to the communicating route described above, we identified (1) a direct and superficial transverse communicating route, and (2) a deep transverse communicating route. The former route was composed of fasciculated large collecting vessels directly connecting the BA nodes to the left venous angle region, lying superficial to the left brachiocephalic vein. The latter route was composed of several large collecting vessels, crossing the brachiocephalic and left common carotid arteries superficially, and merging into the left phrenic nodes directly or occasionally via the pretracheal nodes. These results suggested that IMLs of both sides can closely communicate with each other in the superior mediastinum.