In some ways, certain tumors resemble bee colonies, says pathologist Tan Ince. Each cancer cell in the tumor plays a specific role, and just a fraction of the cells serve as queens, possessing the unique ability to maintain themselves in an unspecialized state and seed new tumors. These cells can also divide and produce the worker cells that form the bulk of the tumor. These queens are cancer stem cells. Now the lab of Whitehead Member Robert Weinberg has created such cells in a Petri dish by isolating and transforming a particular population of cells from human breast tissue. After being injected with just 100 of these transformed cells, mice developed tumors that metastasized (spread to distant tissues). The operational definitio…