Long before a telltale lump is felt and before a tumor is visible on an imaging scan, its cells release and present small fragments of proteins on their surfaces for recognition by the immune system. Because they are unique to the tumor cells, these protein fragments—biomarkers of that specific cancer—hold keys to developing highly specific and reliable molecular tests that detect the cancer at earlier stages, when it is most treatable, as well as associated treatments that precisely target and destroy the cancer.