[Interpretation of D2 radical operation and en bloc mesogastric excision in gastric cancer]

As a surgical oncology concept, complete mesenteric excision has been widely accepted. As to different organs, in addition to the rectum and the colon, the range or the criteria of the so-called complete mesenterium is not yet entirely clear. For the stomach, the mesogastric structure is so complicated, and the embryology and anatomy of the mesogastrium or the perigastric ligaments differed significantly. Even to perform a resection in accordance with the anatomy plane of mesogatrium, the mesogastric plane is still extended as compared to the current standard D2 radical resection. We therefore propose the concept of surgical mesogastrium, which means that the essence of en bloc mesogastric excision (EME) should be surgical mesogastric resection. In clinical practice, we found that a lot of symmetric similarity exists in stomach and colon, the morphological transformation from stomach to the colon can be accomplished to some extent by extension and folding of the stomach, and striking match exists in the morphology, distribution of the blood vessels, lymphatic drainage and mesenterium (mesogastrium or mesocolon). On this basis, we propose the plane of the surgical mesogastrium, which includes the gastrohepatic ligament, hepatoduodenal ligament, hepatopancreatic folds, splenicpancreatic folds, gastrophrenic ligament, gastrosplenic ligament, gastrocolic ligament (supracolic omentum) and omentum. This surgical mesogastric plane coincides with the current plane of D2 radical resection. This paper further discussed the N staging of gastric cancer. By comparative study of the stomach and the colon, we could re-classify the stomach-associated lymph nodes into three groups, the perigastric, the middle and the roots, which may resolve the long-standing controversy between the Eastern and Western regarding this issue. In addition, we also agree with the presence of lymph node metastasis in the plane outside of the surgical mesogastrium, the so-called lateral lymph node metastasis. As for the N staging of gastrointestinal cancer, we must firstly define the lymph node metastasis as mesenteric (mesogastric or mesocolic lymph node) and extra-mesenteric (later lymph node). In case of lateral lymph node metastasis, which should be considered as M1 stage (distant metastasis) unless there is evidence to suggest lateral lymph node metastasis, otherwise extended lateral lymph node dissection should be avoided. In case of mesenteric (mesogastric or mesocolic) lymph node metastasis, classification should be in accordance with the current NCCN guideline, which was divided by the number of lymph node metastasis (N1-N3).