Clusters of cancer cells get around by moving single file

To squeeze through capillaries, tumor cells unfurl and pass through one by one

magnified image of cells squeezing through a capillary

SQUEEZE PLAY  As a clump of stained human breast cancer cells approaches a capillary tube, the cells adjust their formation and their shape to pass through the narrow space. 

S.H. Auet al/PNAS 2016

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In narrow blood vessels, tumor cells go marching one by one.