Most ovarian cysts don’t need to be removed. The majority are functional cysts that form during normal ovulation and disappear on their own within one to three menstrual cycles. A cyst typically needs removal when it grows larger than 5 to 6 centimeters, shows features suspicious for cancer on imaging, causes severe symptoms, or fails to resolve after several cycles of monitoring.
The decision depends on a combination of factors: the cyst’s size, what it looks like on ultrasound, your age and menopausal status, your symptoms, and sometimes a blood test. Here’s how doctors weigh each of those.
Size Thresholds That Trigger Surgery
There’s no single cutoff that applies to every type of cyst, but size is one of the strongest factors. Cysts larger than 5 to 6 centimeters carry a meaningfully higher risk of ovarian torsion, a painful twisting of the ovary that cuts off its blood supply. That risk alone often makes removal worthwhile, even if the cyst looks benign.
For common dermoid cysts (a type that contains tissue like hair, skin, or teeth), surgeons generally use laparoscopy for cysts under about 12 centimeters. Cysts larger than that are more likely to require open surgery through a larger incision. Dermoid cysts also tend to grow slowly over time and rarely resolve on their own, so most are eventually removed regardless of symptoms.
Endometriomas, the chocolate-colored cysts caused by endometriosis, follow a different threshold. The general consensus is that endometriomas larger than 4 centimeters should be removed. Surgery at that size reduces pain, improves fertility, and allows doctors to confirm the diagnosis with a tissue sample. Smaller endometriomas (2 to 4 centimeters) don’t appear to reduce the success of IVF and can often be left in place if they aren’t blocking access to egg-producing follicles.
What Ultrasound Features Raise Concern
Size alone doesn’t tell the whole story. What the cyst looks like on ultrasound matters just as much. A simple cyst, one that’s fluid-filled with thin walls and no internal structures, is almost always benign. The features that raise suspicion for cancer include solid areas within the cyst, multiple internal compartments (called septations), papillary projections growing from the cyst wall, and high blood flow through the cyst tissue on Doppler imaging.
Later-stage ovarian cancers tend to appear as complex masses with a high proportion of solid tissue, often accompanied by free fluid in the abdomen. Cysts with papillary projections are a particular red flag for borderline tumors. When any of these features are present, surgery is typically recommended both to remove the cyst and to get a definitive tissue diagnosis.
How Doctors Estimate Cancer Risk
Rather than relying on any single finding, many doctors use a scoring system called the Risk of Malignancy Index (RMI) to decide how urgently a cyst needs to come out and who should perform the surgery. The RMI combines three things: your menopausal status, what the ultrasound shows, and a blood test called CA-125.
CA-125 is a protein that can be elevated in ovarian cancer. Its normal upper limit is 35 units per milliliter. Levels above that, combined with worrisome ultrasound features, push the risk score higher. The ultrasound portion of the score looks at five specific features: whether the cyst is on both ovaries, whether it contains solid areas, whether it has multiple compartments, whether there’s fluid in the abdomen, and whether there are signs of spread.
Based on the final score, cysts fall into three categories. Low-risk cysts (RMI under 25) can be watched or removed by a general gynecologist. Moderate-risk cysts (RMI 25 to 250) are best handled by a surgeon with specialized training. High-risk cysts (RMI above 250) should be referred to a gynecologic oncologist at a cancer center for a full staging procedure. This scoring system helps ensure that the right surgeon is involved from the start, which improves outcomes if the cyst does turn out to be cancerous.
One important caveat: CA-125 can be elevated for many benign reasons, including endometriosis, pelvic infections, and even normal menstruation. A mildly elevated CA-125 with an otherwise simple-looking cyst doesn’t automatically mean surgery is needed.
Watchful Waiting and When It Ends
For cysts that appear functional, meaning they likely formed during a normal ovulation cycle, the standard approach is to wait and rescan. Most functional cysts resolve within one to three menstrual cycles without any treatment. If a cyst is still present after several cycles of monitoring, it’s unlikely to be a simple functional cyst, and your doctor will recommend further evaluation or removal.
During the watching period, you’ll typically get a follow-up ultrasound to check whether the cyst has shrunk, stayed the same, or grown. Growth during monitoring is a reason to move toward surgery, as functional cysts don’t keep getting bigger.
Cysts After Menopause
The rules change after menopause. Because postmenopausal women are no longer ovulating, any new ovarian cyst can’t be explained by a normal menstrual cycle. That raises the baseline level of concern. Postmenopausal status also increases the RMI score fourfold compared to premenopausal women, reflecting the higher cancer risk in this age group.
That said, not every postmenopausal cyst requires surgery. Updated guidelines from the Royal College of Obstetricians and Gynaecologists (amended in December 2025) state that simple cysts measuring 3 centimeters or less on one ovary don’t require routine follow-up. These small, uncomplicated cysts are common incidental findings on imaging and carry very low malignancy risk. Larger or more complex postmenopausal cysts still warrant closer monitoring or removal.
Emergency Situations
Some cyst complications require immediate surgery, regardless of size or appearance.
Ovarian torsion is the most urgent. It happens when a cyst makes the ovary heavy enough to twist on its blood supply. The hallmark symptom is sudden, severe pain in the lower abdomen, often accompanied by nausea and vomiting. The pain is usually sharp and stabbing, though it can be dull and crampy. It’s most commonly felt throughout the lower belly but can radiate to the thighs, sides, and lower back. If the twisted ovary starts losing blood flow, fever and abnormal vaginal bleeding can develop, signaling that the tissue is beginning to die.
Torsion is diagnosed with a transvaginal ultrasound that shows absent blood flow to the ovary, but the definitive diagnosis happens during surgery. Surgeons typically use laparoscopy to both confirm and treat the twist in the same procedure. If you have a known ovarian cyst and develop sudden severe abdominal pain, that’s a reason to go to the emergency room immediately.
A ruptured cyst can also require emergency intervention. Many small cyst ruptures cause temporary pain and resolve without treatment. But if a rupture causes significant internal bleeding, evidenced by dizziness, rapid heartbeat, or worsening pain, surgical intervention may be needed to stop the bleeding.
What Surgery Looks Like
When removal is necessary, the procedure depends on the cyst’s size, type, and level of cancer suspicion. Laparoscopic surgery is the gold standard for benign cysts. It involves a few small incisions, a camera, and specialized instruments. Recovery is faster, with most people returning to normal activities within one to two weeks.
Surgeons generally try to remove just the cyst while preserving the ovary, a procedure called cystectomy. This is especially important for women who want to have children. In some cases, the entire ovary needs to be removed. This is more common in postmenopausal women, when multiple cysts are present on the same ovary, or when a very large cyst has left little healthy ovarian tissue behind.
Open surgery through a larger abdominal incision is reserved for very large cysts (generally over 12 centimeters) or when cancer is suspected and the surgeon needs full visibility to check for spread. Recovery from open surgery takes longer, typically four to six weeks.