Identity of Biological Sentinel Node metastasis and establishment of Navigation Surgery

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One of the breakthroughs in surgical oncology is that the sentinel lymph node (SN) procedure has opened a window to clinical practice in the field of Gastro-Intestinal (GI) surgery. Our interest is in whether the SN concept is acceptable in GI cancer surgery. SN may be the first lymph node which undergoes influence of factors produced by primary lesion and the initial site of antigen presentation associated with immune responses. In this study, we investigated the biologic features of metastasis including micro-metastasis in SN and evaluated sentinel node concept using both dye and radioisotope in patients with GI cancer.One day prior to surgery, ^<99m>Tc-tin colloid was endoscopically injected into the sub- mucosa near the tumor. Radioisotope uptake in all dissected lymph nodes was measured during and after surgery. Lymph node metastasis and micro-metastasis were examined by RT-PCR using CEA mRNA in addition to Hematoxylin-Eosin staining (HE) and immunohistochemistry (IHC).As a result, sentinel node navigation surgery appears to be clinically acceptable only in early stage of disease that is patients with clinical mucosal or sub-mucosal tumor. A reduction of lymphadenectomy based on sentinel node detection is indicated for such patients. Local immune response in SN with metastasis showed various immune statuses in comparison with non-SN. Although SN concept appear to be acceptable even for GI cancer, the standard procedure and criteria for SN is essential to further improve its clinical application. Another urgent task is to establish a standard method for detection micro-metastasis in SN.