Lymphatic spread, lymph node stations, and levels of lymphatic dissection in gastric cancer

The lymphatic drainage from the stomach is complex and it is difficult to predict the pattern of lymph node metastases from gastric cancer. Nevertheless, there are lymph node stations in which metastases are more frequently observed in relation to the tumor site. Moreover, the frequency of metastasis to various regional node stations depends on the depth of gastric-wall invasion. The Japanese Gastric Cancer Association (JGCA) guidelines have designated four levels of lymph node dissection. D1 lymphadenectomy is a complete dissection of the N1 lymph node group. D1+a dissection is a D1 lymphadenectomy plus resection of station 7, irrespective of the location of the lesion, and additionally of station 8a in tumors of the lower third of the stomach. D1+b dissection is a D1 lymphadenectomy plus resection of stations 7, 8a, and 9. D2 (extended) and D3 (superextended) dissections remove, respectively, lymph node stations of the N1-N2 and N1-N3 lymph node groups. Recently the JGCA revised the definition of Lymphadenectomy: D1 or D2 are now defined according to the type of gastrectomy performed (total/subtotal).