TF is a crucial determinant of metastatic potential but not the TF cytoplasmic domain. (A) Quantitative analysis of experimental pulmonary metastases formed 21 days after intravenous injection of 4 × 10⁵ TF^WT, TF^ΔTail, or TF^O tumor cells into immunocompetent C57Bl/6 mice. The lungs were harvested and fixed in Bouin's solution to better highlight metastatic foci. Each point indicates the total number of pulmonary foci present on all lung lobes from an individual mouse and the horizontal bars represent median values within each cohort. Note that tumor cells carrying TF exhibited markedly greater metastatic potential than TF^O cells (*P < .001, Mann-Whitney U test), but the elimination of the TF cytoplasmic domain had no significant affect on metastasis. (B) Typical appearance of metastatic foci present on individual lung lobes 21 days after intravenous injection of 4 × 10⁵ cells. Note that the metastatic foci formed by TF^ΔTail cells were indistinguishable from TF^WT foci. However, lungs harvested from mice injected with TF^O cells were effectively clear of metastases.