Ex-vivo Sentinel Lymph-node Mapping in Colorectal Cancer

Abstract

Purpose: The presence of lymph-node metastases is one of the most important prognostic factors for patients with a colorectal carcinoma. The sentinel lymph node is the first lymph node that receives afferent lymphatic drainage from a primary tumor, and thus has the highest risk of harboring metastatic disease. Methods: Twenty- eight patients with an adenocarcinoma of the colon or the rectum were investigated. After resection of the specimen in standard oncologic fashion, the specimen was dissected longitudinally along the antimesenteric border, and methylene blue was injected around the tumor submucosally. After 5 minutes, the mesentery was meticulously examined, and blue-stained lymphatics and lymph nodes were carefully dissected and harvested. Results: Sentinel lymph nodes were identified in all cases. The average number of sentinel nodes identified was 3 (range, 1∼6), and the average number of lymph nodes retrieved was 20.8 (range, 6∼42). Of the fifteen patients (53.6%) identified to be positive for lymph-node metastasis 10 showed nonsentinel nodal metastasis without sentinel nodal involvement. No additional isolated tumor cells were found by immunohistochemical staining in 13 patients who had no lymph-node metastasis on conventional pathologic examination. Conclusions: In colorectal cancer, the sentinel-lymph-node sampling method is easy and can be performed for the purpose of finding lymph nodes easily. However, applying the sentinel-lymph-node sampling method for the purpose of minimizing lymph node dissection, as in breast cancer, is not recommended because of the high probability of missing metastasis.