Cancer stem cells. Computer artwork of cancer stem cells (blue) next to a capillary (red). Cancer stem cells (CSCs) are undeveloped cancer cells that, supported by nutrients supplied by the blood vessels, develop into fully functional cancer cells (pink). This association between CSCs and blood vessels has been confirmed in studies of brain cancers. It is thought that the blood vessels help the closest CSCs to remain stem cells, while fuelling the rapid multiplication of cells that is seen in cancer. It is thought that this is related to the growth of new blood vessels around cancers. Some treatments aim to disrupt cancer formation in these blood vessel niches.