Injecting methylene blue into the inferior mesenteric artery assures an adequate lymph node harvest and eliminates pathologist variability in nodal staging for rectal cancer.

PURPOSE

The American Joint Committee on Cancer recommends examination of a minimum of 12 lymph nodes in rectal cancer for accurate staging. Despite this, several studies have demonstrated that nodal harvest is highly variable and often inadequate. This study was designed to determine if staining the nodes with methylene blue dye produced a better and more accurate harvest in comparison with standard pathologic lymph node dissection.

METHODS

Fifty patients with primary resectable rectal cancer were randomly assigned to undergo a standard nodal harvest or a harvest after ex vivo injection of the inferior mesenteric artery with methylene blue. A fat clearance technique was subsequently used to identify the maximum possible number of lymph nodes and metastasis.

RESULTS

The average lymph node harvest was 30 +/- 13.5 in the stained group and 17 +/- 11 in the unstained group (P < 0.001). At least 12 nodes were identified in every case in the stained group. In the unstained group, 7 of 25 cases (28 percent) did not meet the minimum criteria of 12 nodes (P < 0.01). Among the pathologists for the stained group, no difference was found in the harvest (P < 0.05), but variability was detected between the pathologists in the unstained group (P = 0.6). After fat clearance, one case in the unstained group was upstaged, whereas no cases in the stained group were upstaged.

CONCLUSIONS

Staining the lymph nodes with methylene blue dye is an accurate staging technique and reliably produces an adequate harvest.