spontaneous metastasis from tumor transplants of two representative mouse b16 melanoma clones , g3.5 and g3.12 , was examined experimentally to determine whether initial dissemination to the lungs , or secondary systemic spread from established lung metastases , resulted from organ-specific tropism or from nonspecific trapping of circulating tumor cells in capillary beds .
C0027627
metastasis
C0027625
circulating tumor cells