Ductal carcinoma in situ (DCIS) makes up approximately 20% to 25% of all breast cancers detected by mammographic screening programs. Such programs were set up to identify early invasive disease, so the large numbers of all grades of DCIS diagnosed were unexpected and unwelcome. As the natural history of untreated DCIS is largely unknown, its management is controversial; mammogram-detected DCIS is usually treated as if it is cancer, primarily with surgery. Adjuvant treatments may also be offered, which vary from hospital to hospital and from country to country.1 Surgery for DCIS has remained largely unchanged since the 1970s, and mastectomy is now performed more often than is seen with invasive cancer. It is 40 years since the inception of the first breast screening programs, and it is time to question the appropriateness and the outcomes of these management policies for screen-detected DCIS.