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May 2001. Review Article. To the first updating To the second updating To the third updating Only a few studies have investigated the lymphatic flow system of GI cancers from the point of view of the sentinel node concept, which should not be confused with interpretation of previous studies on GI lymphology.
In T1 gastric cancer (depth of cancer invasion limited in the mucosal or submucosal layer ) the incidence of nodal involvement is reported to be as low as 2% to 18% , and in the T2 gastric cancer ( cancer invading the muscular or subserosal layer) that incidence is about 50%.
The authors use the dye method ( IGC) instead of the radionuclide method to detect the Sentinel node (the first node in the regional lymphatic basin that drains the primary tumor). Only T1 and T2 gastric cancers were included in the study because the lymphatic flow would be easily altered when some of the main lymphatic routes were involved and occluded (Hiratsuka). Moreover in the blue dye technique the time of injection of blue dye needs a carefull monitoring, because there is a short window of time during which selective identification of the SN is possible. For this reason Kitigawa et al affirm that a combination of intraoperative endoscopic injection of blue dye and gamma probe inspection (after endoscopic submucosal injection of radioactive tracer, - subserosal injection is difficult for realizing small and superficial lesions, that are not palpable from the serosal side-) is helpful for localizing sentinel nodes in gastric cancer. For confirming the complete resection of sentinel nodes a survey of the abdominal cavity by a gamma-detecting probe is essential (Kitagawa). Hiratsuka reports that the success rate of SN detection was as high as 99%, with only 1 false negative . Because this false-negative case was T2 gastric cancer, it is prudent to state to apply SN biopsy to T1 gastric cancer patients and not to T2 gastric cancer patients. This technique may be very helpful in the less invasive surgical treatments of EGCs ( wedge resection, segmental gastrectomies and EMRs). Because the method of SN detection using IGC is possible under laparoscopic operation it can be combined with the less invasive operations. Hiratsuka hopes for more careful methods for the detection of lymph node metastases in SNs and non SNs (serial sectioning, immunohistochemistry, genetic diagnosis) and for studies on the intraoperative detection of metastases in SN by frozen section or imprint cytology or both (Hiratsuka). In the Tsioulias's study lymphatic mapping was performed in 65 patients with GI neoplasms by injecting 0,5 to 1 ml of isosulfan blue dye around the periphery of the neoplasms. Blue stained SNs were analysed by hematoxilin-eosin staining, multiple sectioning, and cytokeratin immunohistochemistry.
The author underlines that the LM can identify aberrant lymphatic drainage, which may alter the extent of resection.
Moreover there is an inverse relationship between a GI neoplasm' s T stage and the presence of isolated LN metastases. The SN was the only positive node in all T1, 70% of the T2, 26% of the T3 and 20% of the T4 neoplasms. Tsioulias concludes that in the meantime LM with focused examination of the SNs (on serial sectioning and IHC) improves the staging of GI neoplasms and may affect the selection of the patients for adjuvant therapy (Tsioulias). Eventually, according to the Maruyama opinion, the ability to identify a tumor free SN might enable the surgeon to avoid the morbidity associated with radical lymphadenectomy in patients with gastric cancer. But he concludes that it is too early to apply sentinel node biopsy for reducing the extent of lymphadenectomy for gastric cancer because of the complicated anatomy of lymphatic streams from the stomach, and because of frequent skip metastasis and micrometastasis (Maruyama). References
Masahiro Hiratsuka, MD et al. Application of sentinel node biopsy to gastric cancer surgery. Surgery 2001; 129:335-40.
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