Fig. 2

a After the distal bowel transection, the tumor-bearing bowel was pulled out of the abdominal cavity. The carbon nanoparticle suspension was injected into the subserosal layer around the tumor to trace lymph nodes (yellow circle). The point at 10 cm proximal to the primary tumor on the bowel wall was marked (red arrow); b Lymph nodes were mapping and harvested on the fresh specimen. In this study, mesenteric lymph nodes were classified into three parts: main lymph nodes lied along the IMA from the origin of LCA to the root of IMA (MLNs) (red area); superior rectal and perirectal lymph nodes (SPLNs) (blue area); pericolic lymph nodes located beyond 10 cm proximal to the tumor (PCNs) (yellow area). The blue arrow represented the level of 10 cm proximal to the primary tumor on the bowel wall