In Denmark, breast cancer is the most common fatal cancer in women with more than 4700 new cases annually. All patients are treated according to national guidelines developed by the Danish Breast Cancer Cooperative Group (DBCG). Treatment primarily consists of surgical removal of all or parts of the breast and simultaneous removal of one-or lymph nodes in the ipsilateral axilla. Subsequently, there may be a need for additional treatment with chemotherapy, radiation and / or anti-hormonal therapy, in order to reduce the risk of recurrence.