Background: Common tracers for sentinel node navigation surgery are blue dye and technetium-99m-labelled colloids. However, in most esophageal or lung cancer patients, it is impossible to detect the sentinel node among mediastinal nodes by blue dye because of the anthracotic pigmentation of mediastinal nodes. The use of technetium-99m-labelled colloids requires a special facility, while a large hot-spot at the injection site prevents detection of the sentinel node around the primary lesion. To overcome these problems, we investigated the use of fluorescent microspheres (0.1-20 microm in diameter) as tracers in animals and detected fluorescence-positive nodes by a simple ultraviolet light irradiation method.
Materials and methods: Two milliliters of fluorescent microspheres 0.1-20 microm in diameter diluted to 2.5% weight per volume was injected via the tail vein of 30 rats; systemic side-effects were examined. One milliliter of 1.0 microm-diameter microspheres dilution was injected on the backs of 30 rats; local side-effects were examined. A microsphere dilution (0.2 ml, 1.0 microm-diameter microspheres) was injected into the footpad of 18 rats; the lymphatic pathway and drainage were examined. Five milliliters of 1.0 microm-diameter fluorescent microspheres was injected endoscopically into the submucosa of the esophagus, stomach and small and large bowels of 6 domestic pigs, and 5 ml was injected into the subadventitia of the esophagus or subserosa of the stomach, and small and large bowels. Fluorescence-positive lymph ducts or nodes were carefully observed under ultraviolet light irradiation.
Results: No systemic side-effects were observed in rats. Only mild edema and a mild inflammatory reaction were observed on the backs of rats. Fluorescent microspheres 0.1, 0.5 and 1.0 microm in diameter were detected in lymph ducts or nodes of pigs within 1 hour after injection.
Conclusion: Sentinel node navigation surgery with the use of fluorescent microspheres might be feasible and advantageous for patients with esophageal or lung cancer, especially in the mediastinum.