Comparative margins between colorectal carcinoma and peritumoral injected methylene blue.

BACKGROUND: Removal of malignant tumors with free margins is pivotal in oncological surgery. AIMS: To verify the correspondence between the histological growth of colon and rectal adenocarcinomas and how extensively methylene blue diffuses when injected into peritumoral mucosal tissue to understand if the dye margin can guide the correct margin for tumor removal, and also if there is an association between the lymph nodes stained by methylene blue and the presence of metastases. METHODS: This study was conducted with 13 patients with colon or rectal adenocarcinoma. Immediately before the operation, all patients underwent colonoscopy and peritumoral methylene blue injection. Radical resection consisted of the removal of the colon or rectum segment beyond the blue-stained margins, in a monobloc, with the meso and regional lymph nodes. Tumor margins, peritumoral lymphatic density, stained margins, and removed lymph nodes were analyzed. RESULTS: In all operative specimens, tumor-free margins were within the blue-stained area. There was no association between the presence of metastases and the dye in the lymph nodes examined. CONCLUSIONS: Preoperative peritumoral endoscopic injection of methylene blue spreads the dye beyond the limits of colon and rectal adenocarcinomas, determining reliable free margins for tumor resection, but does not indicate the presence of regional lymph node metastases.