Intraoperative methylene blue sentinel lymph node mapping in colorectal cancer

Background: Isosulfan blue is not available for clinical use in Malaysia. This study describes the use of methylene blue as an alternative to isosulfan blue in colorectal sentinel node mapping. Methods: Methylene blue dye was injected around colonic and rectal tumours and the first blue‐stained nodes were suture tagged and harvested after standard colorectal resection. Standard histopathological examination was then carried out to detect nodal metastasis. All negative sentinel lymph nodes (SLN) were subjected to 10 further step sectioning and immunoperoxidase staining for cytokeratin 20 to detect tumour deposits. Results: Thirty‐one patients were enrolled from August 2005 to July 2006. Twenty‐five attempts at identifying the SLN were successful (80.7%). Of the 18 (58.1%) who had nodal metastases (stage III), 3 had negative SLN but positive other lymph nodes (false‐negative rate of 21.4%). In one (4%), the SLN was the exclusive site of metastasis. Conclusion: Methylene blue can be used as an alternative sentinel node marker for rectal cancer (above the peritoneal reflection) and colonic cancer.