The standard breast surgical procedure of locally advanced breast cancer in Norway is mastectomy. There is increasing interest in performing breast conserving treatment (BCT) in locally advanced cases after chemotherapy or hormonal treatment - if there is a partial or complete clinical remission. To increase the evidence for the safety (no residual tumor) of such a procedure directly compared to mastectomy without compromising the safety of the treatment, a breast preserving procedure followed by an immediate mastectomy can be performed within a study. It would then be possible to study the margins after the breast preserving procedure as well as the tumor status in the rest of the breast.