Lymphatic mapping and lymphatic endothelial cell isolation in colorectal cancer patients

Background: Sentinel lymph node (SLN) biopsy has already been established as a common procedure with malignant lymphoma and breast cancer. In colorectal cancer, however, the application of the SLN theory remains uncommon and its clinical significance is also unclear. In addition, the characteristics of the lymphatic vessels that connect SLNs or the lymphatic endothelial cells have been unclear. Our purpose is to determine the feasibility and accuracy of SLN mapping by intraoperative subserosal dye injection and to develop a novel method for the isolation of anatomically defined lymphatic endothelial cells. Methods: SLN biopsy by the subserous dye injection method (patent blue) was conducted in 36 patients with colorectal cancer for which curative resection was possible (stage 0: two cases, stage I: 18 cases, stage II: four cases, stage III: 12 cases), with additional systematic lymph node dissection. Endothelial cells were isolated from lymphatic vessels identified at the time of the SLN biopsy by the collagenase II perfusion method, and we tried to transfer them into a culture system with an endothelial cell‐specific medium. Results: SLNs could be identified in 34 cases, providing a 94.4% detection rate. The total number of resected lymph nodes was 705 and 72 of those nodes were confirmed as SLNs (10.2%). Ten metastasis‐positive nodes were found in SLNs (13.9%), and the mean number of identified SLNs per case was 2.0. No complications or toxicity associated with the dye injection were observed. In addition, cells isolated from the lymphatic vessels removed formed some colonies and the expression of lymphatic endothelial cell‐specific VEGFR‐3 was observed. Conclusion: SLNs mapping using subserosal dye injection is a feasible technique that would make the range of lymph node dissection appropriate for colorectal cancer, which is applicable to cases with advanced cancer. This new method was established to isolate lymphatic endothelial cells from resected lymphatic vessels and to culture them, which may contribute to further study of the molecular mechanisms of lymphangiogenesis.