There are two main causes of breast fibroma: estrogen and congenital factors. 1, excessive stimulation of estrogen: the formation of breast fibroadenoma is related to the vigorous ovarian function and the sensitivity of the body and local breast tissues to excessive stimulation of estrogen; 2. Congenital factors: that is, the abnormal increase of estrogen sensitivity of fiber cells in breast lobules is caused by the large number of estrogen receptors contained in these fiber cells; The above two reasons lead to excessive proliferation of breast fibroblasts, thus forming tumors. The congenital factor, that is, the abnormal increase in the sensitivity of breast lobule fiber cells to estrogen, is caused by the large number of estrogen receptors contained in these fiber cells. Some people call this "seed-soil theory" vividly. Fibroma mostly occurs in ovarian functional period, and rarely occurs before menarche and after menopause. This is enough to prove the importance of estrogen stimulation in its pathogenesis.