A multicentre prospective cohort study will monitor the efficacy and safety of Autologous Fat Transfer (AFT) with pre-expansion. AFT will be evaluated in terms of quality of life, aesthetic result, complications, oncological safety and cost-effectiveness. It follows the BREAST trial, the randomised controlled trial comparing AFT with implant-based reconstruction. In this study, patients all receive AFT.

Inclusion Criteria:

• Female gender
• Age of 18 years and older
• History or in candidate for a mastectomy procedure in the near future
• Patients undergoing preventive mastectomy
• Patients' choice to undergo a breast reconstruction
• Wanting to participate in this study
• Patient is able to wear the external expansion device

Exclusion Criteria:

• Active smoker or a history of smoking 4 weeks prior to surgery
• Current substance abuse
• History of lidocaine allergy
• History of silicone allergy
• 4 weeks or less after chemotherapy
• History of radiation therapy in the breast region
• Oncological treatment includes radiotherapy after mastectomy
• Kidney disease
• Steroid dependent asthma (daily or weekly) or other diseases
• Immune-suppressed or compromised disease
• Uncontrolled diabetes
• BMI>30
• Large breast size (i.e. larger than cup C), unless the patient prefers reduction of the contralateral side towards Cup C
• Extra-capsular silicone leaking from the encapsulated implant from a previous breast reconstruction
• The treating plastic surgeon has strong doubts on the patient's treatment compliance

Breast cancer patients or women who, due to a gene mutation have a significantly high risk of developing breast cancer, decide to undergo profylactic mastectomy.