1. Age In women, the incidence rises with age, rare before the first menstruation and rare before 20 years of age, but the incidence rises rapidly after 20 years of age, higher from 45 to 50 years of age, but is relatively flat, and the incidence continues to rise after menopause, reaching a peak at about 70 years of age. The mortality rate also rises with age, with a gradual increase in mortality after the age of 25, and always maintains an upward trend until old age. 2.Hereditary factors Women who have a history of breast cancer in the first degree of direct relatives in their family have 2 to 3 times the risk of breast cancer than the normal population. The risk of menarche is 2.2 times higher than that of women older than 17 years old if the age of menarche is earlier than 13 years old. 4. Age at menopause The risk of menopause increases for those who are older than 55 years old compared to those who are younger than 45 years old. The risk increases gradually with the postponement of the age of first pregnancy, and the risk is higher for those who have their first birth after 35 years old than for those who have no history of childbirth. 6. Postmenopausal estrogen supplementation Long-term use of estrogen during menopause may increase the risk of breast cancer.