Background: Recently we developed a method to observe pulmonary micrometastasis by labeling cancer cells with green fluorescent protein (GFP). We applied the method for observation of micro-dissemination on the visceral pleura.
Materials and methods: RCN9 rat colon cancer cells labeled with GFP were injected into the pleural cavity of Fischer F344 rats. Six weeks after injection, the chest wall was resected under general anesthesia and the lung surface was observed by real-time confocal laser-scanning microscopy. Blood flow was visualized by intravenous injection of fluorescein isothiocyanate-labeled red blood cells, by which blood flow velocity was measured.
Results: Dissemination was created in 4 out of 5 rats. Fifteen sites of micro-dissemination were observed (mean diameter, 35.8+/-13.3 microm). Blood flow velocity was 114.1+/-26.1 microm/s in the tumor tissue and 183.4+/-35.0 microm/s out of the tumor tissue.
Conclusion: We were able to observe pleural micro-dissemination. Blood flow velocity was significantly lower in the tumor tissue.