Differences in frequency of tumor cells in DLN were well correlated with subsequent macrometastases measureable in lung/liver 23, leading us to conclude that the difference in metastases seen in these two tumor models in mice with altered CD200:CD200R signaling did not reflect altered seeding into the circulation, but rather a differential conditioning of the microenvironment making it permissive for development of metastases. The gene discussed is CD200; the disease is neoplasm.