 From 1993 until he joined the University of Pennsylvania, he was affiliated with the University of Chicago, where he was professor of medicine, a Howard Hughes investigator, and director of the Gwen Knapp Center for Lupus and Immunology Research.Thompson joined the University of Pennsylvania in 1999 as a professor of medicine, the scientific director of The Leonard and Madlyn Abramson Family Cancer Research Institute, and the first chairman of the Department of Cancer Biology.In 2006 he was named director of the Abramson Cancer Center of the University of Pennsylvania and associate vice president for cancer services of the University of Pennsylvania Health System.