Overdiagnosis has been identified in mammographic screening for breast cancer. Long-term follow-up of the Malmo randomized trial of mammography found a persistent excess of 115 breast cancers in the screened group 15 years after the trial was completed (a 10% rate of overdiagnosis). In a letter to the editor, authors not associated with the original study of the data from the randomized clinical trial argued that one-quarter of mammographically detected breast cancers represent overdiagnosis. A systematic review of mammography screening programs reported a overdiagnosis rate of around 50%, which is the same of saying that a third of diagnosed cases of breast cancer are overdiagnosed.