With the help of live imaging, Scientists have been able to track the spread of individual breast cancer cells.
Dr. Erik Sahai, of Cancer Research UK, led the study with laboratory mice, adding hope for new cures to block the metastatic breast cancer route.
Experts followed the movement of the cancer cells from the mouse's primary tumor site.
They marked cancer cells with a "reporter" protein called Transforming Growth Factor beta (TGFb) that glowed blue.
Sahai said: "The results helped us to find the set of genes that are behind the spread of breast cancer-and that the genes need to be first turned on and then off in order for single cancer cells to be able to 'relocate'".
The expert added: "Surprisingly little is known about the way cancer cells spread through the body because it is so incredibly difficult to study," said Sahai.
"In a medium-sized tumor there could be a billion cells-and only a small proportion might break away and spread. So it is like trying to find-and understand-a moving needle in a very big haystack."
The study, published in Nature Cell Biology, was due to be presented at the American Society for Cell Biology in San Diego.