The cancer "Stem cell" theory comes from studies with blood cancers such as leukemiaterm, which are known to grow out of a subset of corrupted hematopoetic stem cells. In some studies, antibodies to the CD44 marker have been able to attach to these cells and block them from attaching to the bone marrow in a new mouse. Here Stanford and Michigan researchers seperated cancer cells from a solid tumor according to the CD44 marker using a technique known as Fluorescense Activated Cell Sorting in which a Flow Cytometerterm physically separates the cells.

Researchers have found a marker on head and neck tumor cells that indicates which cells are capable of fueling the cancer's growth. The finding is the first evidence of cancer stem cells in head and neck tumors.