Some cysts develop as a result of ovulation. These cysts are called “functional cysts,” and they form when the normal release of an egg from an ovary is disrupted and they are the most common type of ovarian cysts. Some cysts may contain tissue formed during egg development and maturation. Endometrioma cysts develop in women with endometriosis, a condition that causes uterine lining tissue to form outside the uterus. If these cysts grow very large, they can result in twisting and torsion of the ovary. Ultrasound and other examinations can be used to identify the type of cysts and its size to decide if and how a cyst should be removed. Cysts that are not removed may be monitored to see if they resolve on their own, if they remain stable or if they begin to grow larger or cause symptoms.