Ovarian cysts are extremely common. Most women who are still menstruating will develop at least one during their lifetime, and many develop them regularly without ever knowing. The majority form as a normal part of the menstrual cycle, cause no symptoms, and disappear on their own within a few months.
How Often Ovarian Cysts Develop
Every month during ovulation, your ovary creates a small fluid-filled sac called a follicle. An egg grows inside this follicle, which then ruptures to release the egg. This process means that a functional cyst, one tied to your normal cycle, can form during virtually any menstrual cycle. Sometimes the follicle doesn’t release the egg and keeps growing. Other times, the sac that held the egg reseals after ovulation and fills with fluid. Both are considered functional cysts, and they’re by far the most common type.
These cysts typically measure under 5 centimeters (about 2 inches) and resolve on their own within two to three menstrual cycles without any treatment. Because they rarely cause symptoms, most go completely unnoticed. When cysts are found, it’s often by accident during an ultrasound or pelvic exam done for an unrelated reason.
Cysts After Menopause
Ovarian cysts aren’t limited to women who are still menstruating. A large cancer screening study that followed women over age 55 found that 14% had a simple ovarian cyst the first time their ovaries were examined with ultrasound. Each year, about 8% of those women developed a new cyst that hadn’t been there before. Among women who had a cyst at their first screening, roughly a third saw it disappear by the next annual exam, and just over half still had a stable cyst one year later. The takeaway: simple cysts are fairly common even after menopause, and most either stay the same size or resolve without intervention.
Types Beyond Functional Cysts
While functional cysts account for the vast majority, other types do occur. These are much less common and tend to behave differently.
- Dermoid cysts contain tissue like skin, hair, or teeth because they develop from embryonic cells. They grow slowly and can persist for years.
- Endometriomas form when tissue similar to the uterine lining grows on the ovary. These are sometimes called “chocolate cysts” because they fill with old blood. They’re linked to endometriosis.
- Cystadenomas develop on the outer surface of the ovary and can grow quite large, occasionally reaching 12 inches or more.
These pathological cysts don’t resolve on their own the way functional cysts do. They’re more likely to cause symptoms like pelvic pain, bloating, or pain during sex, and they more often require monitoring or surgical removal.
Polycystic Ovaries
Polycystic ovary syndrome (PCOS) is a separate condition in which the ovaries develop many small follicles that don’t fully mature or release eggs. Global estimates put PCOS prevalence between 5% and 21% of women of childbearing age, depending on which diagnostic criteria are used. Despite the name, the “cysts” in PCOS are actually immature follicles rather than true ovarian cysts. The condition involves hormonal imbalances that affect periods, fertility, and metabolism, so it’s managed very differently from a standalone ovarian cyst.
How Often Cysts Are Cancerous
The overwhelming majority of ovarian cysts are benign. The risk of cancer is very low, but it does vary by age and by what the cyst looks like on imaging. Simple cysts, which have thin walls and contain only fluid, carry a negligible cancer risk regardless of age. Complex cysts, those with solid areas, thick walls, or internal structures, warrant closer attention.
Among women aged 50 or older with complex ovarian cysts, roughly 6.5% were diagnosed with ovarian cancer within three years, according to a 2019 study. A large UK screening trial found the cancer risk for complex cysts ranged from 0.4% to 6.6%, again depending on the woman’s age and the cyst’s characteristics. For premenopausal women with simple cysts, the risk is a fraction of a percent. Your doctor will use the cyst’s appearance on ultrasound, your age, and sometimes a blood test to determine whether further evaluation is needed.
Do They Come Back After Removal?
Functional cysts can recur because they’re part of normal ovarian function. As long as you’re ovulating, new ones can form. Hormonal birth control that suppresses ovulation reduces this risk significantly.
For pathological cysts that require surgery, recurrence depends on the type. Dermoid cysts, for example, come back in about 3 to 4% of cases after surgical removal. Certain factors raise that rate: being under 30, having a cyst 8 centimeters or larger, or having cysts on both ovaries. A woman with all three risk factors has a recurrence rate around 21%, compared to roughly 3.4% for women without them. Having just two of those factors still elevates risk, with rates between 11% and 21% depending on the combination.
When Cysts Cause Symptoms
Most ovarian cysts produce no symptoms at all. When they do, the most common signs include a dull ache or pressure on the side where the cyst sits, bloating or a feeling of fullness in the lower abdomen, and pain during your period or during intercourse. Larger cysts are more likely to cause noticeable discomfort simply because they take up more space.
Occasionally, a cyst can rupture or twist the ovary (a condition called torsion). A ruptured cyst often causes sudden, sharp pain on one side that fades over hours to days. Torsion is more serious: it cuts off blood flow to the ovary and causes intense, sudden pain along with nausea or vomiting. Torsion is a medical emergency that requires prompt treatment to save the ovary.