Discovery That Cancer Spreading Involves The Sending Out of 'Envoys'

MSNBC reports that scientists at Cornell University in New York have discovered that:

Instead of a cell just breaking off from a tumor and traveling through the bloodstream to another organ where it forms a secondary tumour, or metastasis, [...] the cancer sends out envoys to prepare the new site.
...
tumor cells can mobilize normal bone marrow cells, causing them to migrate to particular regions and change the local environment so as to attract and support a developing metastasis.

The research is reported in Nature.