Postoperative intra-arterial methylene blue injection of colorectal cancer specimens increases the number of lymph nodes recovered.

AIMS: To determine the possible advantage of intra-arterial injection of methylene blue with a view to improving lymph node recovery in postoperative examination of colorectal cancer specimens. METHODS AND RESULTS: Thirty-two colorectal cancer specimens were assigned randomly to either dissection with intra-arterial methylene blue injection or to routine dissection (without methylene blue injection). Immediately postoperatively, the specimens in the staining group were injected intra-arterially with methylene blue dye. The two procedures were compared with respect to the number of lymph nodes recovered. The number of recovered lymph nodes was significantly higher in the intra-arterial methylene blue injection group than in the group investigated with routine procedures (P<0.0001). CONCLUSION: The intra-arterial methylene blue injection method is fairly easy to use postoperatively and increases significantly the number of lymph nodes recovered in colorectal cancer specimens.

The number of identified lymph node metastases increases continuously with increased total lymph node recovery in pT3 colon cancer.

BACKGROUND. The positive correlation between the number of recovered benign lymph nodes and patient prognosis is well established for stage II colon cancer patients. One theory explaining this correlation focuses on potential understaging of cancer specimen, implying that a specimen with few examined lymph nodes is likely to be assigned a lower N-stage than the correct one. Understaging may be the result of an insufficient examination of the specimen post-operatively, whereby few lymph nodes are recovered and potential lymph node metastases are overlooked. This study aims to investigate the association between the total lymph node harvest and the number of lymph node metastases in colon cancer specimen. MATERIAL AND METHODS. We studied the original pathology reports of 649 patients diagnosed with T3 adenocarcinoma of the colon at the Department of Clinical Pathology and Genetics at Linköping University Hospital, Linköping, Sweden between the years 2000 and 2008. Patient demographics, specimen staging data, and lymph node recovery data were collected for each case. RESULTS. We found a positive association between the total lymph node harvest and the number of lymph node metastases per specimen. For every additional recovered lymph node 0.17 (95% CI: 0.15-0.19) metastases were detected (p < 0.001). DISCUSSION. Our results support the conclusion that there is no minimum number of recovered lymph nodes at which an accurate determination of nodal status can be assured. Rather than focusing on a recommended minimum number of nodes, efforts should be shifted towards developing methods assuring that colon cancer specimen are dissected in a standardized way that optimizes the lymph node harvest.