The vast majority of breast enlargements do not turn into cancer, and a very small number of breast enlargements with severe heterogeneous hyperplasia may turn into cancer only after a long period of time. Breast enlargement is not associated with the development of breast cancer. Breast hyperplasia is the unequal qualitative and quantitative changes of the mammary glands under the action of estrogen and progesterone, which leads to the localized breast swelling, pain and lumps in one or both breasts, which are usually more obvious during menstruation, and then gradually disappear after menstrual cycle, and then the swelling, pain and lumps appear again during the next menstruation. Breast cancer, on the other hand, is an abnormal proliferation of breast cells, whose proliferation is not regulated by normal genes, and both of them occur by different mechanisms and are different in nature. Early stage of breast hyperplasia is usually not cancerous, but with the aggravation of breast hyperplasia, severe heterogeneous hyperplasia of breast tissue and so on will appear. The severe heterogeneous hyperplasia of the breast is a precancerous lesion, and patients with severe heterogeneous hyperplasia can progress to cancer, the exact time varying from person to person. 80% of women will experience breast hyperplasia in their lives, and there is no need to be nervous about it; regular checkups are sufficient.