Using a specific laser scanning method, the establishment of metastasis during cancer can be visualized in the brain, reports in this week's Nature Medicine.

Brain metastasis commonly occurs in patients with cancer and is often fatal. Frank Winkler and colleagues have now used a technique known as multiphoton laser scanning microscopy to see the single steps of metastasis formation in real time. They were able to track the fate of individual metastasizing cancer cells in relation to blood vessels deep in the mouse brain over minutes to months.

The scientists established a series of essential steps ― arrest of the cancer cells at blood-vessel branching points, exit from the blood vessel, persistent contacts between the cell and capillaries and, finally, growth of the metastasis around the blood vessel.

The ability to visualize the establishment of brain metastases inside the living brain will provide new insights into their development and will enable scientists to measure response to therapies.