Another possible harm of screening is overdiagnosis. This means finding something on a mammogram that is breast cancer or has a chance of becoming breast cancer, but is such a low-risk type of tumor that it would never have caused any health problems if left alone. Instead, because it was found on mammogram, standard cancer treatment, such as surgery and radiation therapy, is recommended. In cases of overdiagnosis, these treatments are unnecessary and costly and can have both physical and psychological side effects. It is difficult to know exactly how often overdiagnosis happens, but some studies estimate that 1 in 5 breast cancers found on mammograms are overdiagnosed and lead to unnecessary treatment.