What is an ovarian cyst?

The definition of a cyst is a fluid-filled sac. Cysts can occur anywhere in the body. With PCOS, women can develop "cysts" due to eggs not being released over time. The follicles keep growing and form multiple "cysts." These may be described as appearing like a "string of pearls" in an ultrasound image.

Despite the name, women with PCOS don't need to have ovarian cysts. Women without PCOS may develop cysts related to other reasons. The most common type of ovarian cyst is called a functional cyst.

These cysts are described as "functional" because they often develop during the menstrual cycle. There are 2 types:

  • Follicular cysts: These usually go away on their own in 1 to 3 months. These form when an egg doesn't get release as expected, so the follicle keeps growing.
  • Corpus luteum cysts: These also usually go away on their own. These form after the follicle ruptures and releases the egg (ovulation). The follicle reseals and fluid starts to buildup within it. They can enlarge and cause pain, bleed, or twist the ovary. Fertility medicines used to promote ovulation (such as clomiphene) can increase the chances of developing these type of cysts.

Ovarian cysts can also be related to endometriosis, or formed from the outer surface of the ovary (cystadenomas), or formed with non-ovarian tissue (dermoid cysts).

Sources: Office of Women's Health, Department of Health and Human Services. American College of Obstetrics and Gynecology.