Ex vivo intra-arterial methylene blue injection in the operation theater may improve the detection of lymph node metastases in colorectal cancer

IntroductionLymph node (LN) assessment after colorectal cancer resection is fundamentally important for therapeutic and prognostic reasons. LN positivity is an indication for adjuvant treatment. This study aimed to investigate whether immediate postoperative intra-arterial methylene blue (MB) injection (MBI) into colorectal cancer specimens by a surgeon in the operating room could improve the rate of total LN and metastatic LN recovery for pathological examination.Materials and methodsSeventy-three consecutive patients prospectively enrolled between January 2011 and December 2013 were assigned to the methylene blue (MB)-stained group and compared with 107 controls in the unstained group.ResultsThe median number and range values of metastatic LNs, the number of LNs <0.5 cm, the total number of LNs harvested, and the number of cases with LN metastasis were significantly different between the MB-stained and MB-unstained groups (p = 0.016, p = 0.010, p = 0.025, and p = 0.006 respectively).ConclusionsImmediate MBI (fresh, unfixed samples) by a surgeon in the operating room may result in a significant increase in the number of metastatic LNs diagnosed and the number of cases with positive LNs. Shifting of the injection from the pathology laboratory to the operation theater would be a good alternative whenever the operation theater is not the area located as the pathology department.