Preliminary study for sentinel lymph node identification with Tc-99m tin colloid in patients with esophageal or gastric cancer.

The purpose of this study is to determine whether a lymph node identified with high radioisotope (RI) activity is a sentinel node. We studied 26 patients with either esophageal or gastric cancer whose preoperative imaging studies showed no lymph node metastasis. Before surgery, Tc-99m tin colloid was injected via endoscopy into the submucosa. In lymph nodes dissected at surgery, RI activity was measured by a scintillation counter, and metastatic status was examined by hematoxylin-eosin staining. The number of dissected nodes was 45 +/- 15 (mean +/- SD) per patient, and the number of nodes with high RI activity was 4 +/- 1. Nodal metastasis occurred in 11 of 26 patients. In 9 of these 11 patients, metastatic foci were found in one or more nodes with high RI activity. In one of the 2 remaining patients, endoscopic clipping was applied just above the injection sites, and in the other patient, the tumor invasion was beyond the muscle layer. For further analysis, the case with clipping was excluded, and only those in which the tumor invasion was confined within the muscle layer were evaluated. Six of 18 patients in this analysis showed nodal metastasis. Each of the 6 patients had at least one node that showed high RI activity and that was positive for metastasis. We conclude that when tumor invasion remains within the muscle layer, lymph nodes with high RI activity can be regarded as sentinel nodes.