Usefulness of sentinel node mapping in resected colorectal cancer

Background: It has been shown by increasing evidence that the sentinel node (SN) is at greatest risk of harboring metastatic cancer cells. We investigated whether or not SN identification could be used as a method for determining the proper extension of lymph node dissection in colorectal cancer. Methods: In 41 surgical patients with colorectal cancer, resected specimens were injected submucosally with blue dye in four quadrants. Blue lymphatic channels were identified in the mesentery and followed to the blue-stained lymph nodes (defined as SNs), which were then harvested. The specimens were fixed in formalin and subsequently analyzed. Ten clinicopathological factors and survival were compared between true positive and false negative patients. Results: Of the 41 patients studied, 34 (82.9%) had SNs, and 137 SNs were identified from among 1135 nodes harvested. A total of 73 lymph nodes in 21 patients were found histologically to display evidence of metastatic disease. As a result, the false negative rate was 17.6%, the specificity rate was 100%, and the sensitivity rate was 62.5%. Between true positive and false negative patients, there were no significant differences in the 10 clinicopathological factors or in survival. Conclusion: SN identification by ex vivo mapping appears to be useful as a method for determining lymph node dissection in colorectal cancer.