During surgery for ovarian cancer, all attempts are made to get every last cancer cell. A new system may make that job easier. Prior to surgery, patients are injected with a fluorescently tagged version of folic acid (also called vitamin B9). Ovarian cancer cells tend to take in lots of folic acid so they become marked with the fluorescent molecule. During surgery, special lights and software are used to identify cancer cells. The method has been used in a small sample of humans with good success. The ultimate test, whether the patients do better, is still to be determined.