| Background: Surgical resection is the most effective treatment for patients with gastric cancer. At present, radical gastrectomy with regional lymph node dissection remains the standard procedure, but extended lymph node dissection maybe increase complications and mortality of operation, also it may accelerate relapse. SN biopsy is a new kind of technique raised and developed in recent years. At present, the application of this technique to gastric cancer is just under investigation, and it is worthy to be studied further. Micrometastatic disease in lymph node is hard to be detected with H&E staining but can be confirmed only by immunohistochemical (IHC) methods, thus with IHC staining is often used to examin nodal micrometastasis in patients with gastric cancer.Objective: The selective patients underwent standard radical gastrectomy, at the same time blue dye-guided technique was used to locate the sentinel lymph nodes, to explore the feature of lymph node metastasis, to examine the feasibility of SN biopsy and its reliability in predicting lymph node status in patients with gastric cancer and to evaluate the role of IHC staining with cytokeratin monoclonal antibody in SN biopsy.Methods: Proper patients with gastric cancer were selected for research. After laparotomy and exploration of the abdominal cavity, Methylene blue was injected into the subserosal layer at 4 different sites around the primary tumor, with each site 0.8-1.0ml and the total dose 2.0-4.0ml. Several seconds after the injection, the blue-stained lymph vessels could be observed and along with the lymph vessels some blue-stained lymph nodes (SN) could be identified. All the SNs were removed before gastrectomy. After the operation, the SNs were examined by H&E staining and IHC staining with cytokeratin monoclonal antibody (AE1), and the non-sentinel lymph nodes(n-SN) and the stomach dissected were subjected to conventional pathological examination (by H&E staining).Results: i. Lymph node metastases were found in 55 of 76 patients with a metastasis rate of 72.4 %( 55/76). Metastasis rate in early gastric caner was 30%(3/10), which was much lower than that in advanced gastric caner (78.8%, 52/66; p<0.05), and a similar result appeared between T1+T2 group (47.1%, 8/17) and T3-I-T4 group (79.7%, 47/59, p<0.05). Orderly progression of tumor cells within the lymphatic system was found in 92.7% patients (51/55) and 97.2 %( 213/219) but "skipping metastasis" was found only in 2.8% nodes (6/219) of 7.3% patients (4/55). ii. SNs have been detected in 66 patients with a detection rate of 86.8%. Tumor size was the only factor to affect the detection rate. iii. In the 66 cases, a total of 81 SNs were detected (1-3 per patient). Majority (78) of the 81 SNs were distributed along the greater or lesser curvatures, i.e., they belonged to Nj nodal station. Only 3 (3 cases) belonged to N2 station, and 2 were observed only in No.7, the other only in No.8a. there was no SN observed in N3 station. iv. Lymph node metastases were found in 45 of 81 SNs on H&E staining, and 35 cases with metastasis, so the lymph metastasis degree is 55.6% (45/81) and the lymph metastasis is 53.0% (35/66); As so as the method of IHC staining was concerned, the lymph metastasis degree is 61.7% (50/81) and the lymph metastasis is 59.1%(39/66). The difference between the lymph metastasis degree and between the lymph metastasis were insignificant with the two different examinations (p>0.05) . The 5 negative SNs with H&E staining showed micrometastasis (MM) microscopically with IHC staining, v. In the 66 patients with a successful identification of SNs, The sensitivity of the SN status in diagnosis of the lymph node status of the patients was 72.9% (35/48), and accuracy and false-negative rate were 80.3% (53/66) and 27.1% (13/48). With increasing depth of invasion, the lower sensitivity and accuracy and the higher false-negative rate were observed.
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