Ductal carcinoma in situ (DCIS) is a premalignant lesion in the breast. It is often asymptomatic and diagnosed by screening mammography. DCIS is treated in line with low-risk invasive breast cancer including mastectomy or breast-conserving treatment plus radiotherapy, implicating a risk of both physical and psychological side effects. Since only a part of DCIS lesions develop into invasive cancer, some women suffer from overtreatment. However, it remains yet to be identified, in which subgroup of women with DCIS treatment can safely be omitted. We need to know more about the natural course of DCIS and develop tools to tailor treatment individually.