Validation of lymphatic mapping in colorectal cancer: In vivo, ex vivo, and laparoscopic techniques

Background: The use of lymphatic mapping (LM) is being investigated to impr ove the staging of colorectal cancer (CRC) and thereby identify patients wh o might benefit from adjuvant chemotherapy. This study evaluated in vivo, l aparoscopic, and ex vivo approaches for the ultrastaging of CRC. Methods: Seventy-five CRC patients were enrolled in a study of LM with peri tumoral injection of isosulfan blue dye. LM was undertaken during open colo n resection (OCR) in 64 patients, during laparoscopic colon resection (LCR) in 9 patients, and after specimen removal (ex vivo) in 2 patients. Ex vivo LM was also undertaken in 6 patients after unsuccessful in vivo LM. All no des were examined by hematoxylin and eosin (H&E) staining; in addition, sen tinel lymph nodes (SNs) were multisectioned and examined by immunohistochem ical staining with cytokeratin (CK-IHC). Results: At least one SN was identified in 72 patients (96%). In vivo LM id entified SNs in 56 of 64 (88%) patients undergoing OCR and in 9 of 9 (100%) patients undergoing LCR, Ex vivo LM was undertaken as the initial mapping procedure in 2 cases of intraperitoneal colon cancer and after in vivo LM h ad failed in 6 cases of extraperitoneal rectal carcinoma; an SN was identif ied in 7 of the 8 cases. Focused examination of the SN correctly predicted nodal status in 53 of 56 OCR cases, 9 of 9 LCR cases, and 6 of 7 ex vivo ca ses. Multiple sections and CK-IHC identified occult micrometastases in 13 p atients (17%), representing 10 OCR, 1 LCR, and 2 ex vivo cases. Conclusions: LM of drainage from a primary CRC can be accurately performed in vivo during OCR or LCR. Ex vivo LM can be applied when in vivo technique s are unsuccessful and may be useful for rectal tumors. During LCR, colonos copic injection can be used to mark the primary tumor and define the lympha tic drainage so that adequate resection margins are obtained. These LM tech niques improve staging accuracy in CRC.