Statement: The difference between cohort 1 and 2 of the primary trial is assesment by ultrasonography and the insertion of an additional negative pressure drain for patients in cohort 2.
Primary_evidence: INTERVENTION 1:    Single Drain   Insertion of a single drain: A negative pressure drain will be inserted below the lower flap directing to the axilla in the single drain group.   Ultrasonography after removal of the drains: One day after removal of the drains seroma under the flaps and in the axilla will be examined by ultrasonography.   Insertion of a single drain: A negative pressure drain will be inserted below the lower flap directing to the axilla.   Ultrasonography after removal of the drains: One day after removal of the drains seroma under the flaps and in the axilla will be examined by ultrasonography. INTERVENTION 2:    Double Drain   Insertion of double drains: Two negative pressure drains will be inserted into the axilla and below the lower flap in the double drains group.   Ultrasonography after removal of the drains: One day after removal of the drains seroma under the flaps and in the axilla will be examined by ultrasonography.   Insertion of double drains: Two drains will be inserted into the axilla and below the lower flap in the double drains group.   Ultrasonography after removal of the drains: One day after removal of the drains seroma under the flaps and in the axilla will be examined by ultrasonography.