Over the past 20 years, a large number of clinical subgroup studies have demonstrated that there is no statistical difference in recurrence and survival rates for early-stage breast cancer with breast-conserving surgery and postoperative radiotherapy compared to conventional radical surgery. With the development of diagnostic techniques and the increase of early stage patients, the number of cases of breast-conserving surgery has been increasing in some developed countries in the West. In the United States, in 1993 alone, more than 50% of patients underwent breast-conserving surgery, and in Japan and Hong Kong, China, this percentage reached 40% and 30%, respectively. However, in mainland China, this percentage is still very small. The main reasons are that the traditional aesthetic concept of breast conservation is not strong (the difference of cultural background), the doctors’ understanding of breast conservation has not yet been fundamentally changed (insufficient update of doctors’ professional knowledge), not many early cases and the lack of radiotherapy equipment (the real medical conditions and socio-economic development level). Indications for breast-conserving surgery: ① primary tumor diameter <3-4cm; ② ipsilateral axillary lymph nodes not touched or touched but not considered metastasis; ③ single tumor, far from nipple and areola. ④The ratio of breast to tumor volume is moderate. If the breast is too small, it is meaningless to preserve the shape; if it is too large, fibrosis after radiotherapy will incur obvious asymmetry on both sides of the breast. Absolute contraindication: multicentric breast cancer. Including X-rays suggesting diffuse distribution of malignant calcifications. Relative contraindications: ① primary foci ≥ 5 cm axillary lymph nodes ≥ 2 cm; ② metastatic lymph nodes ≥ 4; ③ tumors with short disease duration and rapid multiplication time; ④ breast cancer in the expectant stage; ⑤ patients with collagenous vascular lesions and severe radiofibrosis and fat necrosis after breast irradiation. Due to the widespread use of preoperative chemotherapy, the indications for breast-conserving surgery have been relaxed in recent years, such as breast-conserving surgery can be considered for patients with large masses that can be significantly reduced to less than 3 cm after chemotherapy. If the lump is in the areola area of the nipple, it can also be considered for reconstruction after excision. The basic requirements of surgery: ① local paracentesis of the lump of more than 3cm (controversial), large segmental resection or quadrant resection, requiring no cancer cells on pathological examination of the cut edge, which is the key to no recurrence after breast-conserving surgery. ②The range of axillary lymph node dissection should in principle be no less than the traditional dissection range. The incision usually starts from the outer edge of the pectoralis major muscle and crosses the axilla to the anterior edge of the latissimus dorsi muscle. If the mass is located externally, an incision may be chosen together with the primary site of resection. In foreign countries, axillary lymph node dissection may be performed in conjunction with resection of the primary focus, or the procedure may be postponed, or may not be performed, depending on the results of axillary lymph node biopsy.