Suitable indices for evaluating the intensity of tumor metastasis in a mouse experimental metastatic model

We investigated the time course of developmental changes of tumor metastasis in mice intravenously inoculated with B16-F10 melanoma cells. The mice showed a normal blood profile at 7 and 14 days after the injection, while at 21 days they developed severe anemia and thrombocytopenia. The number of metastatic lung nodules in the mice at 7 and 14 days after the cell injection was 68 +/- 12 and 326 +/- 39 (mean +/- S. E. of 5 mice), respectively, while it could not be accurately counted at 21 days owing to a fusion of the nodules. The wet weight and the melanin content of the lung markedly increased at 21 days. These results suggest that an abnormal blood profile, lung weight and the melanin content of the lung are suitable indices for the late stage of the experimental metastatic model, while the number of lung nodules is suitable for the early stage.