OBJECTIVETo investigate the feasibility of ex vitro sentinel lymph node (SLN) mapping with methylene blue staining and its clinical value of predicting regional lymph node metastasis in colorectal cancer.

METHODSMethylene blue (1 ml) was injected submucosally around the tumor immediately after resection. After 2-5 minutes, the first blue-dyed lymph nodes, sentinel lymph nodes (SLNs), were harvested for pathological examination, and compared with the pathological results of other lymph nodes.

RESULTSOf the total 32 patients, 57 SLNs were successfully identified in 30 patients with an average of 1.9 nodes per person. The successful labeling rate was 93.8% (30/32). Among the 13 patients with positive SLNs, there were 5 patients with positive non-SLNs and 8 patients with negative Non-SLNs. Among the 17 patients with negative SLNs, there were 15 patients with negative non-SLNs and 2 patients with positive Non-SLNs. The accuracy of SLNs for regional lymph node metastasis was 93.3% (28/30), the false negative rate was 11.8% (2/17), and the specificity was 100% (13/13).

CONCLUSIONSEx vitro sentinel lymph node mapping with methylene blue staining in colorectal carcinoma is technically feasible and can effectively reflect the metastatic situation of regional lymph nodes.