The most common malignancy among women worldwide, the fastest increasing incidence, the most self-recognized, the most X-rayed, the most biopsied, and the largest social expenditure. Incidence: 1.2 million new cases and 400,000 deaths per year worldwide. Shanghai, China: Age of onset around 45. 56.2/100,000 in 2000. 20/100,000 in the early 70’s soon developed to 56.2/100,000. The incidence of breast cancer in Shanghai is related to the westernized lifestyle. Peak incidence: After the age of 45 to 50 years, there are two peaks: 45-50 years and 65-70 years for postmenopausal elderly patients. Possible causes: 1. Genetic factors: BRCA1/BRCA2 gene carriers are more likely to develop the disease. 2.Environmental factors. 3. High risk factors: family history of breast cancer, early menarche (less than 12 years old), late menopause (more than 55 years old), no childbirth, age at first full-term birth more than 31 years old, history of breast cancer on one side, history of surgery for benign breast disease (atypical hyperplasia), hormone replacement therapy. How to prevent: 1. Healthy lifestyle: reduce high fat and high animal protein intake. Increase the intake of fresh vegetables and fruits and vitamins. Exercise and control body weight. 2.Healthy heart. 3. Avoid long-term use of drugs and foods containing large amounts of estrogen. 4.Treat related benign diseases. 5.Self-examination and regular follow-up. Time of physical examination: before menopause, about 10 days after menstruation. After menopause, physical examination at any time. Suspicious symptoms of physical examination: 1.Lumps. 2, nipple depression. 3. Nipple overflow. 4. Skin changes. 5. Asymmetry of both breasts. Ultrasound once every 6 months to once a year, and mammography once a year for those who are older than 40 years old. Puncture will not cause metastasis and spread of tumor. Breast cancer treatment: surgery, radiotherapy, radiotherapy, endocrine therapy, targeted therapy. Surgery: modified radical surgery, breast-conserving surgery, sentinel lymph node biopsy, breast reconstruction. Radiotherapy: radiation damages cellular DNA to kill cancer cells to prevent local recurrence. Chemotherapy: Breast cancer is a systemic disease and can be treated with intravenous or oral chemotherapy. Anti-cancer drugs enter the systemic blood circulation to attack cancer cells that may be present throughout the body and prevent distant metastasis, and neoadjuvant chemotherapy can be administered. Endocrine therapy: triamcinolone acetonide 5 years Regular review of endometrium. Use letrozole, anastrozole, exemestane after menopause. However, calcium supplementation and exercise are required.