what causes cysts in breasts

Breast cysts are noncancerous (benign), fluid-filled sacs that can develop in the breasts. The exact cause of breast cysts is not fully understood, but they are believed to develop as a result of hormonal changes, particularly from monthly menstruation and natural hormonal fluctuations. Experts think that breast cysts may occur when fluid fills an empty milk duct, and they are thought to be a part of the normal life cycle of the breast, associated with changes in hormone levels. Breast cysts are common and usually harmless, with most not requiring treatment. They are more common in women before menopause, typically under the age of 50, but can be found in women of any age, and they are not usually associated with an increased risk of breast cancer