A substantial proportion of patients with breast cancer develop distant metastases after years and sometimes even decades of latency. Mina Bissell and colleagues have found that the expression of thrombospondin 1 by vascular cells that are part of a stable vasculature promotes breast cancer cell quiescence. However, in sprouting neovasculature, this effect is lost and breast cancer cell growth is promoted through the expression of transforming growth factor β1 and periostin by endothelial tip cells.