What are the symptoms of breast cancer? Breast cancer has no symptoms at the early stage and it is easy to be delayed. As the disease progresses, breast lumps will gradually appear. If you find nipple invagination, skin depression, breast deformation and underarm lumps, it is not early stage anymore. At this time, cancer cells can be transferred to the whole body through blood or lymphatic system. Breast cancer prone population It is very rare for breast cancer to occur in women at the age of 20, and the incidence of breast cancer gradually increases from the age of 35. The first peak of breast cancer among women in China is between 45-50 years old and the second peak is between 60-65 years old. Although the exact cause of breast cancer is still uncertain, according to epidemiological findings, the following factors are closely related to breast cancer: 1. family history of breast cancer; 2. previous breast cancer on one side; 3. benign breast disease, especially with atypical hyperplasia; 4. not having children; 5. not breastfeeding after childbirth; 6. first full-term pregnancy at age 30; 7. age of menarche at 12 years or menopause after age 55; 8. 8, obesity, or excessive fat intake, alcoholism, smoking; 9, repeated exposure to various types of radiation; 10, long-term oral or injectable estrogen.