Cyst of the ovary, follicular: A fluid-filled sac in the ovary, the most common type of ovarian cyst. It results from the growth of a follicle. A follicle is the fluid-filled cyst that contains an egg. In some cycles, this follicle grows larger than normal and does not rupture to release the egg. Normally it resolves with simple observation over the course of days to months.

Most ovarian cysts are never noticed by the woman and resolve without her ever knowing that it was there. When a cyst causes symptoms, pain is by far the most common presentation.

The pain from an ovarian cyst can be caused from rupture of the cyst, rapid growth of the cyst and stretching, bleeding into the cyst, or twisting of the cyst around its blood supply.

The diagnosis of an ovarian cyst is usually conformed (or made) by ultrasound, the best imaging technique for ovarian cysts.

The treatment of these tumors is dependent upon the woman's age, the size of the cyst, and its appearance on ultrasound. Treatment can consist of simple observation.

If the tumor is causing severe pain, or if it is not resolving or is suspicious in any way, then it can be removed through laparoscopy or, if needed, through an open laparotomy (bikini incision).

Once the cyst is removed, it is sent to the pathologist who looks at it under a microscope to make the final diagnosis as to the type of cyst it is.

With follicular cysts of the ovary, the outcome is usually excellent.