ScienceDaily (Sep. 18, 2009) — Penn State College of Medicine researchers, in collaboration with colleagues at the University of Southern California, have taken an important step in understanding the role of stem cells in development of liver cancer. Using a unique approach that involves study of individual cells, the team, led by C. Bart Rountree, M.D., has demonstrated for the first time a population of cancer stem cells in the liver prior to tumor formation.