The exact cause of breast cancer is still inconclusive. Because the etiology of breast cancer involves a variety of possible factors, it can only be said that the occurrence of breast cancer may be related to some of the following factors: Genetic susceptibility: Clinical data from family history surveys indicate that the incidence of breast cancer is higher in those with a family history than in those without a family history. Especially for those with bilateral breast cancer and those with younger age of onset, the risk of breast cancer in these women is 9 times higher than that of the average woman, which may be related to genetic factors that make them have susceptibility to breast cancer and endogenous causes of the lesion. Endocrine factors: Endocrine disorders are one of the causes of breast cancer. Due to the abnormal stimulation of endocrine hormones in the breast for a long time, it leads to cancer of breast tissue, among which estrogen and luteinizing hormone are the two endocrine hormones most closely related to breast malignancy. This has been successively confirmed by many clinical, pathological and physiological scientists. Viral factors: Viral particles can be transmitted through breastfeeding and lead to breast cancer, which has been confirmed through more animal experiments. Other factors: low immune function against cancer and suppression of immune function of anti-cancer factors; as well as traumatic stimulation of breast and radiation damage have been reported to predispose to breast cancer.