| BackgroundAlthough gastrectomy with extended lymph node dissection(D2) is the standard surgical treatment for gastric cancer in many countries, the prognosis benefit and the rational extent of lymphadenectomy is still controversial. The current staging procedures employed for gastric cancer is also problematic. The development of sentinel lymph node(SLN) concept brings hope to solve these problems. As initially described for cutaneous melanoma and breast cancer, lymphatic mapping(LM) of SLN can be applied universally as an accurate means of identifying the most likely metastastic lymph nodes from primary solid tumors via the lymphatics. Sentinel lymph node biopsy(SLNB) may offer potentially good reliability on which to plan the extension of lymphadenectomy for tumors. Up to date, however, only a few reports has been available on the SLNB for gastric cancer in which different methods for identifying SLN are used and different results are obtained. Many surgeons are still skeptical about the feasibility of SLNB and its accuracy in predicting the status of non-SLN lymph nodes in gastric cancer. ObjectivesThe current study consisting of five parts is attempted to investigate systematically the SLN of gastric cancer and its purposes are: (1) Gastric cancer patients with solitary lymph node metastasis are analyzed retrospectively in order to examine the distribution of SLN and to provide useful information for intraoperative SLN detection; (2) to probe the feasibility of ex vivo SLN mapping in gastric cancer and provide with pathologist a simple and effective technique to improve the accuracy of staging gastric cancer; (3) To assess the applicability of method for detecting SLN in gastric cancer with blue dye and its value of predicting the absence or presence of lymph node metastases; (4) to evaluate the validity of SLN mapping with radioisotope and y probe -guided approach in gastric cancer and its potential role in diagnosing the tumor status of entire region lymph nodes; (5) to investigate the advantage of combining the dye-directed andradioguided methods for identifying SLN in early gastric cancer(EGC) and the clinical significance of limited surgery in SLN-negative EGC . Methods1. Retrospectively studying the distribution of SLN: 86 gastric patients who had only one lymph node metastasis were regarded retrospectively as patients with a possible sentinel lymph node metastasis, and the clinicopathological data of these patients were analyzed, especially the location of the solitary metastases in relation to the primary tumors were studied.2. Ex vivo SLN mapping in gastric cancer: Gastric cancer patients undergoing a gastrectomy with D2 lymphadenectomy were included in this study. The ex vivo technique was used either as a primary LM procedure in 19 patients, or secondarily for in vivo LM in 3 patients. After en block resection of gastric cancers, specimens were immediately taken to a side table or delivered to the Department of Pathology, 1% patent blue in a volume of 4ml was then injected subserosally at four sites around the tumor, or submucosally in four quadrants of the lesion after opening the stomach. Blue lymphatic channels were identified in the omenta and followed to the blue-stained lymph nodes(SLNs), which were then harvested and submitted for pathologic examination. Blue-stained nodes that were negative by hematoxylin and eosin(HE) staining were further analyzed by cytokeratin immunohistochemical staining with two-step Elivision method. The diagnostic accuracy, sensitivity, negative predictive value and false-negative rate were calculated according to definitions previously reported.3. Intraoperatively identifying SLN in gastric cancer with dye-directed method: 52 patients with T1-T3 gastric cancer were enrolled in the present study. After laparotomy and exploration of the abdominal cavity, 4ml of 1% patent blue violet were injected subserosally at 4 different sites around the primary tumor , or submucosally in four quadrants of the lesion using...
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