Scope of tumor resection was simulated according to the MR imaging data. After meticulous design, the investigators created the personalized porous biodegradable scaffold and printed by 3D printer, using porous PCL biomaterials. During operation, the biodegradable scaffold was implanted into the defective cavity after tumor resection. Safety indicator, cosmetic outcome and autologous compatibility were evaluated.

3D image reconstruction and printing Magnetic model images data were firstly produced by Siemens Trio Tim 3. 0 T MRI. The relative scanning parameters were adjusted as follows: layer thickness 0.9mm; pixel pitch 0.625 mm. In general, the thicker the layer thickness and pixel pitch, the better resolution and the more similar reconstructed model the investigators will get. The MRI data were then imported into Mimics 17.0® [Materialise, Leuven, Belgium] for 3D reconstruction of the targeted area. In this software, the investigators can adjust threshold value to acclimatize to segment tumor area. After that, 3D models were calculated and output as .stl files. According to the requirements of surgical planning, the scope of tumor resection was created after 2 cm expansion of the tumor area, that is, the filling scope of the implant. Next, the investigators designed the personalized porous degradable scaffold. In order to guarantee no significant differences and deformation of the implanted scaffold, the investigators used the contour of tumor resection as the boundary of the scaffold, with flexible porous structure as the units of the scaffold. Boolean operation can help to achieve this target. Finally, the printing of the personalized porous biodegradable scaffold was carried out. Biologically active material PCL was selected and the deformation and degradation time were set for 2 years by adjusting the molecular weight of PCL. Theoretically, PCL with the molecular weight above 65,000 can stably exist for 2 years in vivo, and then it will gradually degrade into H2O and CO2.The PCL material was put into the 3D printer, which was developed by the State key laboratory for mechanical manufacturing systems engineering of Xi'an Jiaotong university. The personalized porous biodegradable scaffold was completed after printing and removing supports.

Procedure In this study,the investigators produced the bio-implant at least 10 days before surgery. Before surgery, the printed bio-implant has been prepared and obtained full sterilization. Simply, under general anaesthesia, lumpectomy and sentinel-lymph-node biopsy was performed firstly, followed by 3D-printing scaffold transplantation.

Inclusion Criteria:

• Breast cancer patients
• Tumor sized 3 cm to 6 cm
• ECOG score 1-2
• Multiple diffuse lesions in one quadrant
• Written informed consent

Exclusion Criteria:

• Triple negative breast cancer patients
• Participant in another clinical study
• Pregnancy and breastfeeding
• Patients with nipple infringement
• Inflammatory breast carcinoma
• Paget's disease
• Serious operative contraindication
• Contraindication for MRI