Afferent and efferent lymph-collecting vessels of the submandibular nodes with special reference to the lymphatic route passing through the mylohyoid muscle

Background. Although metastasis of cancer in the oral region to the submandibular node is well described, there has been no anatomic representation of lymph vessels penetrating the oral floor and draining into the node. Materials and Methods. Ninety specimens were obtained from formalin-fixed, donated cadavers. Histologic observations using serial sections followed the macroscopic observations. Results. In 19 of 90 specimens, we found afferent collecting lymph vessels exiting from the mylohyoid surface and draining into the preglandular submandibular node. In 3 of the 19 specimens, collecting vessels passing through the narrow muscle gap with or without arteries, veins, and nerves were identified histologically. The postglandular submandibular node was not evident in the drainage route. Conclusions. Although it carries a low incidence, because of the direct lymphatic route or pathway between the oral region and preglandular submandibular node, the pathologically positive supraomohyoid node sometimes seems to be found even in elective neck dissection. However, we speculate that sentinel node investigation would reveal the much more critical role of the jugulodigastric node not only as the actual sentinel node but also as the common terminal node along the various drainage routes from the oral region.