Cysts on the ovary are a common cause of acute pelvic pain. It typically occurs in menstruating women but can also occur in postmenopausal women. A cyst is a fluid filled structure like a balloon that can enlarge as more fluid accumulates. The size can range from a few millimeters up to 10 centimeters or larger. The term “cyst” is a general description used for a growth on the ovary. The other term used is mass but the term cyst is less intimidating. Masses or cyst can also arise within the fallopian tubes and thus adnexal masses refer to growths in the tube or ovary.

Most ovarian cysts resolve spontaneously and those that don’t are usually benign (not cancerous). Simple ovarian cyst results from normal ovarian function. Thus they can be found in most women and are a common incidental finding on pelvic imaging. The desire to diagnose ovarian cancer in its earliest state results in an increased surveillance of ovarian cysts. It is important to remember that the incidence of ovarian cancer is around 1-2 %. The lifetime risk of surgery for a suspected adnexal malignancy is 5-10% but only 13-21% are found to be a cancer.

The ovary is the female reproductive organ and thus is the reservoir of the reproductive cells called the oocyte or egg. The released egg when fertilized by a sperm then develops into an embryo and then a fetus. The oocytes develop from follicles, which are stored in the stroma of the ovary. At birth a female infant has over 400,000 follicles. After puberty these follicles are capable of proliferating in an attempt to become a mature egg. Each month a few follicles grow and usually one will mature enough to be released as an egg. The rest will regress.

As the follicles develop they can trap fluid and this can develop into a cyst. Thus follicular cysts are the most common type of cyst found. They usually are multiple and small. Once an egg is released (ovulation), the cells at this site continue to proliferate and produce hormones. This proliferation will stop if fertilization doesn’t occur. If fertilization does occur the growth continues and produces hormones to support the pregnancy until the placenta is capable of taking over this function. The site of ovulation is called the corpus luteum and a corpus luteal cyst can also occur.

The surface of the ovary can develop inclusion cysts. These are typically quite small, usually a few millimeters. These are a common finding in postmenopausal women. Finally, benign tumors can develop from any cells of the ovary. They typically do not resolve and will continue to grow, eventually requiring surgical removal. A common type is the dermoid cyst (or mature teratoma), which can grow as large as 15 centimeters or more. Endometriosis on the ovary can grow and swell into a chocolate cyst, called an endometrioma. They can be managed medically but sometimes will require surgical resection.

An adnexal mass can also be from the fallopian tubes. Tubal cysts, a hydrosalpinx or a tubo-ovarian abscess are common conditions that present as an adnexal mass. An ectopic pregnancy can also present as a mass. In this situation an accurate diagnosis should be made as soon as possible to avoid the life-threatening emergency of a ruptured ectopic.

Ovarian cysts are common and are typically an incidental finding on ultrasound. The vast majority will resolve spontaneously and rarely are they a malignancy however close observation is recommended so there is an opportunity to intervene early if a malignancy is suspected.

I hope this article has provided you with information that will help you make wise choices, so you may:

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