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

The use of lymphatic mapping (LM) is being investigated to improve the staging of colorectal cancer (CRC) and thereby identify patients who might benefit from adjuvant chemotherapy. This study evaluated in vivo, laparoscopic, and ex vivo approaches for the ultrastaging of CRC.

Seventy-five CRC patients were enrolled in a study of LM with peritumoral injection of isosulfan blue dye. LM was undertaken during open colon 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 nodes were examined by hematoxylin and eosin (H&E) staining; in addition, sentinel lymph nodes (SNs) were multisectioned and examined by immunohistochemical staining with cytokeratin (CK-IHC).

At least one SN was identified in 72 patients (96%). In vivo LM identified 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 had failed in 6 cases of extraperitoneal rectal carcinoma; an SN was identified 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 cases. Multiple sections and CK-IHC identified occult micrometastases in 13 patients (17%), representing 10 OCR, 1 LCR, and 2 ex vivo cases.

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 techniques are unsuccessful and may be useful for rectal tumors. During LCR, colonoscopic injection can be used to mark the primary tumor and define the lymphatic drainage so that adequate resection margins are obtained. These LM techniques improve staging accuracy in CRC.