Objective:The presence of lymph node metastases is an important factor in the prognosis of gastric cancer patient. Therefore, the precise identification of sentinel lymph nodes (SLN) in these patients is critical. In this work, we investigated the feasibility and preciseness by injection of99mTc-sulfur colloid (SC) 2 hours before operation after general anesthesia, instead of one day before surgery.Methods:Thirty-one patients of gastric cancer diagnosed as T1-T3 were enrolled in this study. During operation, a SLN was defined as those containing 10 times more radioactivity than surrounding tissue with a hand-held gamma probe and removed. All the patients underwent radical gastrectomy with extended lymphadenectomy. All resected nodes were examined postoperatively by routine H&E stain and those negative SLNs were examined with further cytokeratin immunohistochemistical staining.Results:The incidence of metastasis was significantly higher in SLNs than in non-SLNs (x2=67.48, P<0.001). The overall sensitivity, specificity and accuracy of the SLN status in the diagnosis of the lymph node status of the patient were 86.36%, 100% and 96.77%, respectively. The positive predictive value and negative predictive value of SLN biopsy were 100%, and 75.0%, respectively. SLNs were used to diagnose the lymph node status with 100% accuracy in the T1 group. In the T2 and T3 groups, the sensitivity, specificity, and diagnostic accuracy were 92.3%, 100%, and 94.44%, 60.0%, 100%, and 66.66%, respectively. Most of the SLNs were located in the #1, #2, #3, #4, #5, and #6, except in 3 patients (9.68%).With cytokeratin immunohistochemical staining, lymphatic pathologic staging in 1 patient was upstaged.Conclusion:SLN biopsy with the above approach is a feasible and accurate diagnostic procedure for detecting lymph node metastasis in patients with gastric cancer, which is painless, noninvasive, easily accepted by patients and suitable for extensive clinical applications.