Mastectomy and breast-conserving surgery (BCS) are common procedures for treating breast cancer at present. The discovery rate of tumors 2 cm or less in size has risen with the increase in the number of women who receive breast physical examinations, and because of the wider usage of preoperative chemotherapy, BCS has become possible. As a result, the number of women undergoing BCS has increased, whereas the number of those undergoing mastectomy has decreased. However, if radical cure or good cosmetic results cannot be achieved, mastectomy is often offered to patients. Recently, patients have come to expect good cosmetic results after BCS, and because breast reconstruction with implants is now covered by health insurance, it is possible to perform it with mastectomy with the help of plastic surgery if patients desire. Oncoplastic surgery is now the focus of public attention, because it differs from conventional BCS in that it results in no deformity, since the defect created by wide resections is filled with a local tissue flap. It is psychologically important for patients to have satisfactory cosmetic results after BSC.