Detection Of Sentinel Lymph Node In Gastric Cancer And Its Clinical Significance

Objective: Objective of this search clearly predicts the metastasis status of lymph nodes, increases the veracity of clinical stage in patients of gastric cancer through detection of sentinel lymph node. Patients with negative lymph node metastasis can void usual extended lymph node dissection, and patients with positive lymph node metastasis can benefit from extended lymph node dissection. Methods: From February 2004 to April 2005, there were 50 patients with gastric cancer who were enrolled in this study and treated in our hospital. Their diagnosis was obtained through endoscopic pathological inspection. All of them were performed gastrectomy or total gastrectomy. In parallel with the gastrectomy, all patients received an extended lymph node dissection. After laparotomy and exploration of the abdominal cavity, those with distal metastasis, invasion of neighboring organs, history of abdominal operation, and obesity were excluded from this research. The method of biological dye is used to locate the sentinel lymph node during operation: after incision of peritoneal cavity, Methylene blue was injected to the subserous layer at 4 different sites around the primary tumor, each site with 0.8～1ml and the total dose is 3～4ml. After the injection, the blue-stained lymph vessel can be observed and along with the lymph vessel some blue-stained lymph nodes can be detected within 5～10 minutes, and the blue-stained lymph nodes that appear first will be defined as sentinel lymph node. In the operation, all sentinel lymph nodes was examined by the method of frozen section. After the operation, all sentinel lymph nodes and non-sentinel lymph nodes were subjected to normal pathological examination, sentinel lymph nodes were subjected to Immunohistochemical stain again, using Sreptavidin-Peroxides technique. The dissected stomach was subjected to normal pathological examination to determine the depth of the tumor invasion. Results: Of 50 patients, the stained SLN could be identified in 49 patients. Success rate is 49/50(98%). In all 49 cases, 102 SLNs were detected, each case with 1～4. After operation,912 non-SLNs were found in the dissected stomach. So in all 1014 lymph nodes were checked. The major part of SLNs were in the N1 (46/49 98.33%) and the minor were in N2 (3/49 1.67%). Only one was observed in the 7th group. Of 49 patients with a successful identification of SLNs, 15 were found to have lymph node metastases in SLNs, 9 in both SLNs and non-SNLs, 6 in SLNs alone; 34 were not found to have lymph node metastases in SLNs, 8 of 34 were found to have lymph node metastases in non-SNLs. The sensitivity of the SLN status in diagnosis of the lymph node status of the patient was 15/23(65.22%). Specificity and diagnostic accuracy were 26/26(100%) and 41/49(83.67%). The false-negative rate was 8/23(34.78%). In the 13 patients with T1 cancer, 5 were found to have lymph node metastases in SLNs only; 8 were not found to have lymph node metastases in SLNs, and not in non-SLN. SLNs status could diagnose the lymph node status of the patients with accuracy 13/13, 100%( sensitivity 5/5, 100%; specificity 8/8,100%), and there was no false-negative case. In the 23 patients with T2 cancer, 8 were found to have lymph node metastases in SLNs, 7 in both SLNs and non-SLNs, 1 in SLNs alone; 15 were not found to have lymph node metastases in SLNs, 1 of 15 was found to have lymph node metastasis in non-SLNs. The sensitivity of the SLN status in diagnosis of the lymph node status of the patients was 8/9(88.89%), specificity was 14/14(100%), diagnostic accuracy was 22/23(95.65%). The false-negative rate was 1/9(11.11%). In the 13 patients with T3 cancer, 2 were found to have lymph node metastases in SLNs, 2 in both SLNs and non-SLNs; 11 were not found to have lymph node metastases in SLNs, 7 of 11 were found to have lymph node metastases in non-SLNs. The sensitivity of the SLN status in diagnosis of the lymph node status ofthe patients was 2/9(22.22%), Specificity was 4/4(100%), diagnostic accuracy was 6/13(46.15%), The false-negative rate was 7/9(77.78%). Conclusions: 1.The method of injecting methylene blue around the primary tumor is a feasible method that can locate SLN during operation. 2.The method of immunohistochemical stain and normal HE stain can accurately verdict the metastasis status of lymph nodes ,and it can be thought as an effective ,economical,sensitive pathological examination method. In the patients with T1,T2 gastric cancer SLN can clearly predict the metastasis status of lymph nodes, increase the veracity of clinical stage in patients of gastric cancer through detection of sentinel lymph nodes. In the patients with T3 gastric cancer,SLN can not clearly predict the metastasis status of lymph nodes. 3.Patients with negative lymph node metastasis may void usual extended lymph node dissection, and patients with positive lymph node metastasis may benefit from extended lymph node dissection through detection of sentinel lymph node. 4.Lymph node metastases are regular in gastric cancer,but in some cases, "skip metastases"can exist in lymphatic drainage basin.