Sentinel node mapping for node positive oral cancer: potential to predict multiple metastasis.

Objective: The objective of this study is to evaluate lymph node mapping for clinically positive neck metastasis using a sentinel node navigation technique. Methods: 99mTc-labeled rhenium sulfide was injected as a radiotracer in 10 patients with squamous cell carcinoma of the tongue. After surgery, lymph nodes were classified into two categories according to the radioactive accumulation: nodes with radioactivity and nodes without radioactivity. The ratio of the metastatic area (RMA) of pathologically metastatic lymph nodes was measured. Results: In 5 of 10 cases, all of the metastatic nodes had radioactive accumulation. In one case with three metastatic nodes, radioactivity was not detected in one metastatic node, although it was detected in the other two nodes. In the other four cases, there were no radioactivities in any of the metastatic nodes. RMA of lymph nodes in which radioactivity was not detected was higher than that of lymph nodes in which radioactivity was detected. None of the nodes in which radioactivity was detected was fully occupied by metastatic carcinoma cells. In each case, in comparing the clinically positive lymph nodes, RMA of the nodes in which no radioactivity was detected was higher than that of the nodes in which radioactivity was detected. Conclusion: The principle behind the sentinel node technique is detection of the node that has the most lymph flow from the tumor through injection of the tracer into the circumference of the tumor. When no radioactive accumulation is found in clinically positive metastatic lymph nodes, the possibility of metastasis to other lymph nodes should be highly suspected.