Ovarian cyst: A fluid-filled sac in the ovary.
The most common type of ovarian cyst is called a follicular 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.
Other types of ovarian cysts can contain blood (hemorrhagic or endometrioid cysts).
Still other types of ovarian cysts are called dermoid cysts (or ovarian teratomas). These bizarre (usually benign) tumors can contain many different body tissues such as hair, teeth, bone, cartilage, etc.
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, or it could include blood tests such as a CA-125 to help evaluate the growth for the potential of cancer. It should be noted that the interpretation of the CA-125 blood test has limitations in that women without cancer may have an elevated blood level, and those with cancer may have a negative blood test.
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.
The outlook (prognosis) depends on the nature of the ovarian cyst. With virtually all benign cysts, the outcome is excellent.