The spread of individual cancer cells is more life-threatening than is the metastasis of a group of cells.

While single cells can travel through the blood circulation to sites throughout the body, groups of cancer cells are limited the lymphatic system, which keeps them local.

Advanced microscopy and analysis, said Sahai, allows researchers to investigate cell signaling "live" while observing individual cancer cells make the crucial transition to metastasis. It gives science a closer look at a process that has been largely hidden.

"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."

Source: American Society for Cell Biology