The development of breast cancer is the result of a combination of endogenous and exogenous factors, and the more mature views in etiological research are as follows 1. Reproductive factors: over-nutrition, overweight and obesity and early physiological development may lead to early menarche, and unreasonable intake of sex hormones in long-term diet and hormone replacement therapy may increase the age of menopause, which greatly increases the risk of breast cancer. 2. This results in a high-fat, high-calorie, low-fiber diet. 3, mental factors: modern women are prone to depression such as tension and anxiety, impatience and anger, loneliness and depression, etc. Long-term emotional stimulation will lead to disruption of the body’s vital rhythm and dysfunction of the neuroendocrine system, which will lead to imbalance of the internal environment and decrease of immunity to breast cancer. 4. Environmental factors: long-term consumption of alcohol and tobacco, being in a polluted environment and being close to radioactive substances. 5. Genetic factors: having cancer in the family. Breast cancer diagnosis Nodules and lumps in the breast may be the early manifestation of breast cancer, especially painless lumps must be examined in hospital. The incidence of breast cancer in China is 17.09/100,000, and in some areas it is as high as 30/100,000, but the cancer of cystic hyperplasia of breast is as high as 6.5%, and the cancer of atypical hyperplasia of the third level is as high as 33%. Therefore, if the symptoms and nodules of breast enlargement do not change after taking medication for more than one month, you should go to the hospital for further examination and treatment. Experienced doctors can basically diagnose after examining the lump, but ultrasound and mammography have to be performed again, and sometimes other tests such as ductoscopy, non-surgical pathological biopsy such as needle core, vacuum assisted biopsy, cytology biopsy, and surgical pathology have to be performed to confirm the final diagnosis. There are various surgical methods, including breast-conserving treatment after resection of early-stage breast cancer, single excision of breast, and modified radical treatment for mid-stage breast cancer. Nowadays, the research on breast cancer is very advanced in the world and the treatment methods are constantly updated, the survival rate of breast cancer is increasing, early detection and early treatment is the most crucial.