An ovarian cyst is a liquid-filled sac that develops on one of the ovaries. It is common for most women to develop at least one cyst during their lifetime, as a result of the normal function of the menstrual cycle. There are different types of ovarian cysts, such as dermoid and endometrioma cysts. However, functional cysts are the most common. The two types of functional cysts include follicle and corpus luteum cysts. Although experts are not yet sure why some women develop ovarian cysts and others do not, they have identified several risk factors. Some risk factors are smoking; family history of ovarian, breast or colorectal cancer; obesity; women who have never been pregnant; women who did not breastfeed their children; and certain medications, such as fertility drugs or hormone replacement therapy. Most ovarian cysts do not cause any signs or symptoms and they go away on their own. This is particularly true of functional cysts. However, a large cyst can cause some disco...