Ovarian cysts

What is an ovarian cyst?

Ovarian cysts are fluid-filled sacs or solid pockets that can form in or on your ovaries. Anyone born with ovaries can develop an ovarian cyst. They are common and can affect you at any age. Certain conditions such as endometriosis and polycystic ovary syndrome (PCOS) can make it more likely that you may develop ovarian cysts.

The most common type of ovarian cyst is formed during ovulation. Cysts are more common in premenopausal women, because ovulation stops after menopause. Although it’s less common, postmenopausal women can still get ovarian cysts.

How common are ovarian cysts?: Ovarian cysts are common. About 1 in 10 women will need surgery to remove an ovarian cyst in their lifetime. Exactly how common they are is hard for researchers to track because ovarian cysts often develop and disappear without you knowing. They may be found during unrelated medical tests or scans.

Types of ovarian cysts

Ovarian cysts can be benign (non-cancerous), malignant (cancerous) or borderline. In borderline ovarian cysts, the cells look different to healthy cells, but they are not considered cancerous. Most ovarian cysts are non-cancerous.

An ovarian cyst may be:

Simple – a fluid-filled cyst with a thin wall
Complex – a cyst that contains thicker fluid or blood, walls within the cyst (septations) or solid areas.

Simple cysts

Simple cysts are the most common type of ovarian cyst. They can happen in both those who have gone through the menopause and those who haven’t. Simple cysts are generally non-cancerous and disappear without the need for treatment.

Functional cysts

A functional cyst is a type of simple cyst. They are benign (non-cancerous) and develop as part of the menstrual cycle. If you haven’t gone through the menopause, you may have a functional cyst as these are the most common type of ovarian cyst. You may also hear them be called a follicular or luteal cyst.

Each month during the menstrual cycle, an ovary grows a small sac filled with fluid, like a cyst, called a follicle. Follicles contain hormones and burst to release an egg during ovulation each month. Functional cysts can form:

if a follicle doesn’t release an egg (you don’t ovulate) or
if the fluid that has been protecting the egg inside the follicle doesn’t burst and shrink after the egg is released, as it usually does.

Functional cysts do not usually cause symptoms and tend to disappear after a few months.

Complex cysts

Complex cysts are usually caused by abnormal cell growth. They are less common than simple cysts. They also have a higher risk of being cancerous than simple cysts, but most complex cysts are non-cancerous.

There are different types of complex ovarian cysts. These include:

Cysts caused by endometriosis, known as endometriomas. These cysts are filled with blood. Endometriosis is a condition where the lining of the womb (endometrium) grows outside of the womb. This may be in the ovaries, the fallopian tubes (tubes that the eggs released from the ovaries travel through to the womb) or elsewhere in the pelvis (the lower part of your tummy). It can sometimes be found in areas outside the pelvis, but this is rare.
Dermoid cysts, which grow from a type of ovarian cell called germ cells. These cells develop into eggs. Dermoid cysts are also called mature teratomas. These cysts often contain hair, teeth or fat cells within them. They are usually non-cancerous (benign) but may need to be removed surgically.

How are ovarian cysts diagnosed?

An ultrasound is the most common way of scanning for ovarian cysts. Usually this is a transvaginal ultrasound. This type of ultrasound involves the health care professional inserting a small probe into your vagina to get a clearer image of your pelvic organs. The probe will be in a protective cover and lubricated with warm jelly.

Other scans can be used to get more information:

MRI: a scan that uses magnetic and radio waves
CT: a scan that uses x-ray.

What tests can I have to investigate the cyst? 

Sometimes more tests are needed to decide if an ovarian cyst needs treatment. Whether or not tests are needed depends on the size and type of cyst and if you’ve gone through the menopause or not.

Ovarian cyst tests in premenopausal women

If you haven’t gone through the menopause and have a simple cyst that is less than 5cm in size, you may not need further investigation. These cysts often go away after a few months.

If a simple cyst is between 5-7cm, you should be offered a follow-up appointment. This is usually an ultrasound scan a year later. If the cyst is larger than 7cm you may be offered more tests such as an MRI scan to see if treatment is needed.

If your cyst is complex, an MRI scan and more blood tests will usually be needed to check if the cyst is cancerous. It is still rare for a complex cyst to be cancerous, but there is a higher risk than with simple cysts.

These blood tests include a CA125 blood test. CA125 is a protein in your blood. Ovarian cancer can sometimes cause a raised CA125 level. A normal level of CA125 is usually less than 35 units per millilitre (u/ml). But CA125 levels are not a reliable test for everyone. Some women may not have raised CA125 levels even when diagnosed with ovarian cancer, whilst others may have naturally high levels in their blood for other reasons.

Ovarian cyst tests in postmenopausal women

If you’ve gone through the menopause and the cyst measures less than 1cm, you’re not likely to need any more tests.

Age increases your risk of developing ovarian cancer. So current guidelines from the Royal College of Obstetrics and Gynaecology recommend that all postmenopausal women with an ovarian cyst larger than 1cm have a CA125 blood test and an ultrasound to check for ovarian cancer.

The results of your CA125 test, ultrasound scan and your menopausal status will be combined to work out the chance of the cyst being cancerous. This is called an RMI (Risk of Malignancy Index). It helps medical teams to decide whether you need further tests.

Depending on your results, you may be referred to a gynaecological cancer specialist for more tests. This is a doctor who specialises in cancers of the female reproductive system. A team of specialists will review your test results to decide what treatment you may need. They are called a multi-disciplinary team (MDT).

Treating ovarian cysts

If and how your cyst is treated will depend on:

the type of ovarian cyst
the size of the cyst
if the cyst is causing symptoms and
whether you’re premenopausal or postmenopausal.

Although most simple ovarian cysts will disappear on their own, some ovarian cysts need to be removed with surgery. Surgery is usually considered if the cyst is large or growing and could cause complications, pain or discomfort.

Treatment for premenopausal women

In most cases doctors recommend watchful waiting because cysts often disappear on their own. Watchful waiting means you won’t have treatment straightaway, but you may be offered an ultrasound scan within a few months to check if the cyst is still there or if it has gone.

Complex cysts or larger cysts may need surgery (an operation) depending on the results of the ultrasound or MRI scans and blood tests.

Treatment for postmenopausal women

If you have been through the menopause, you may be offered both ultrasound scans and blood tests over the course of a year to monitor the ovarian cyst. Most people are discharged from follow up after a year as long as there is no change in the size or appearance of the cyst.

If there is a risk that your cyst is cancerous, or your cyst is growing or complex, you may need surgery to remove the cyst.

Surgery for ovarian cysts

An ovarian cyst may need to be removed with surgery if:

there are concerns that the cyst is cancerous or could become cancerous. Surgery is the best way of finding out exactly what the type of cyst you have. Once it’s been removed it can be examined by a pathologist. This is a specialist doctor who looks at the tissue under a microscope to make a diagnosis.
the cyst is large and/or causing pain and discomfort. Occasionally, if a cyst is large enough it can cause ovarian torsion. This is when an ovary becomes twisted with nearby tissues, such as a fallopian tube, which can cut off its blood supply.

If you need an operation your doctor will explain in detail what they will need to do. You will be asked to sign a consent form once you are sure that you understand the operation. Make sure that you ask any questions that you may have before signing your consent form.

Surgery is carried out under general anaesthetic. This is where you are given medicine to send you to sleep so you can’t feel any pain and don’t move during the operation.

There are different types of operations used to remove ovarian cysts:

Keyhole surgery (a laparoscopy) is used to remove most cysts. During this type of operation small cuts are made in your abdomen (tummy) and the surgery is carried out using a fine flexible tube with a camera on the end.
Open surgery (a laparotomy) is used to remove larger or suspicious cysts. A larger cut is made in your abdomen (tummy) during the operation.

Depending on the situation, an operation can be to:

remove the cyst only. This is called a cystectomy
remove the ovary, fallopian tube and cyst. This is called a unilateral salpingo-oophorectomy
remove both fallopian tubes, both ovaries and the cyst. This is called a bilateral salpingo-oophorectomy.

The type of operation you have will depend on the appearance of the cyst and whether you’ve gone through the menopause. It’s unlikely that your test results will suggest the possibility of cancer. But if ovarian cancer is suspected you will be offered a different operation to remove the cancer.

More information

The NHS has more information about diagnosing and treating ovarian cysts.
Royal College of Obstetricians & Gynaecologists has more information about ovarian cysts before the menopause.
If you have any questions or would like to discuss this information, give our specialist nurse-led support line a call on 0808 802 6000.

On this page: