Calling an illness “prostate cancer” or “breast cancer” doesn’t get to the core of the problem. That classification system—using organs and parts of bodies—is far too broad. Even categorizing cancers based on a specific cell type within an organ, bone or muscle, such as the lining of the kidney, isn’t enough. The truth is that cancer cells are more genetically diverse than that and are driven by the genetic mutations they carry. And that determines the course of treatment a patient will undergo. Mehmet Toner, Helen Andrus Benedict Professor of Surgery at Massachusetts General Hospital, is mentioned. Keith Flaherty, associate professor of medicine at Massachusetts General Hospital, is quoted.