Methylene blue-assisted lymph node dissection in colon specimens: a prospective, randomized study.

Recently, we introduced ex vivo intra-arterial methylene blue injection into the inferior mesenteric artery as a novel method to improve lymph node (LN) harvest in rectal cancer. We have now adapted this method to the other segments of the colon. A total of 60 cases were enrolled. Primary LN dissection was followed by fat clearance and a secondary dissection. The mean +/- SD primary LN harvest differed highly significantly with 35 +/- 18 and 17 +/- 10 LNs in the methylene blue-stained and unstained groups, respectively. Primary insufficient LN harvest occurred in 8 cases of the unstained group and in only 1 case of the methylene blue-stained group (P = .0226). After secondary dissection, upstaging was seen exclusively in the unstained group. The time/LN ratio differed significantly with 0.9 and 0.6 min/LN in the unstained and methylene blue-stained groups, respectively. Intraarterial methylene blue injection is recommended as a routine technique in the histopathologic study of colon cancer.