Validation and feasibility of ex vivo sentinel lymph node "mapping" by methylene blue in colorectal cancer.

ABSTRACT

BACKGROUND/AIMS: There are currently divided opinions about the usefulness of sentinel lymph node mapping in colorectal carcinoma. This technique can potentially be useful in determining the volume of resection, reducing the number of analyzed lymph nodes limited to sentinel lymph nodes, and re-staging when metastases are detected in the sentinel lymph node. The aim of this study was to examine the feasibility of postoperative sentinel lymphatic node detection (hereinafter referred to as ex vivo sentinel lymph node mapping) in patients with colorectal carcinoma. METHODOLOGY: The clinical study included a total of 58 patients. Thirteen patients were intraoperatively excluded. Ex vivo sentinel lymph node mapping by methylene blue was used in this study to detect the lymphatic micrometastases. Lymph node preparations were also stained with hematoxylin eosin, followed by immunohistochemical staining of serial sections. RESULTS: Ex vivo sentinel lymph node technique was performed in 45 patients, successfully in 41/45 (91.1%). 22.9 lymph nodes (range 11 to 43) and 1.7 sentinel lymph node (range 0 to 4) were resected and stained. Sentinel lymph node staining was negative in 15/45 patients (33, 3% false negative results). CONCLUSIONS: Limited histopathology analysis by ex vivo sentinel lymph node mapping can not replace a complete histological analysis of all resected lymph nodes.