Dermoid Cyst of the Ovary: Is It Serious and Does It Need Surgery?

A dermoid cyst of the ovary is a slow-growing, almost always benign growth that contains mature tissue such as skin, hair, fat and sometimes teeth. Its medical name is mature cystic teratoma. It does not usually go away by itself, so the main decisions are about its size, symptoms and whether it should be removed or watched.

Cleveland Clinic describes dermoid cysts as the most common benign ovarian germ cell tumour. They form from the cells that would normally make eggs, which is why they can contain tissues from different parts of the body. The cyst is not a baby or a pregnancy; it is a collection of mature tissue and fluid.

Many are found by chance on an ultrasound done for another reason, including pregnancy scans. Cleveland Clinic notes they occur in both ovaries in 10% to 15% of cases, so the scan usually looks at the other ovary too.

A large cyst can make the ovary twist on its blood supply (ovarian torsion), and a cyst can also burst. Both need prompt assessment. Seek emergency care through local services if you have any of the following:

• Sudden, severe pain in the lower tummy or pelvis, especially with nausea or vomiting.
• Pain with fever, which can suggest infection after a cyst leaks.
• Dizziness, light-headedness, fainting, rapid breathing or cold, clammy skin.
• Unusual vaginal bleeding together with pelvic pain.
• If you are pregnant, or could be, and have pelvic pain or bleeding, tell the service so pregnancy causes can be checked as well.

Almost never. Cleveland Clinic states that cancerous change happens in less than 2% of dermoid cysts. It lists a higher risk when the person is over 45, when the cyst is growing quickly, or when it is larger than 10 centimetres across.

The word teratoma can sound alarming. Cleveland Clinic separates mature teratomas, which are usually benign and most common during the reproductive years, from immature teratomas, which are cancerous and a different condition. A dermoid cyst is the mature type.

The RCOG leaflet on cysts before the menopause states that almost all cysts at this stage of life are benign. If your report uses words such as solid areas, rapid growth or uncertain features, ask how the team has judged them rather than assuming the worst or the best.

Ultrasound is the main test. Dermoid cysts often have a typical look because fat, hair and calcium appear differently from simple fluid. Cleveland Clinic says experienced sonographers recognise them nearly 100% of the time. A transvaginal scan, an abdominal scan or both may be used.

MRI is sometimes added when ultrasound does not give enough information. For complex cysts, the team may also offer blood tests to help work out the cyst type; our guide to high CA-125 explains why that marker can rise for many reasons. For a wider view of how simple and complex cysts are described on scans, see our ovarian cyst ultrasound guide.

Size matters mainly because larger cysts carry a greater risk of complications. Cleveland Clinic explains that a large dermoid cyst can twist the ovary, and without treatment the ovary can be damaged. Larger cysts are also more likely to rupture.

Cleveland Clinic gives a rough guide that removal may be recommended when a dermoid cyst is larger than about 5 centimetres, causes symptoms, or might be cancerous. This is a general guide, not a strict cut-off. Your team will also weigh your age, symptoms, pregnancy plans and how the cyst looks.

A rupture is not always dramatic. The body can sometimes absorb leaked contents, but leakage can also cause inflammation or infection that needs emergency care.

Not every dermoid cyst needs an operation straight away. If the cyst is small and not causing problems, the team may suggest monitoring with regular ultrasound scans so any growth or change is picked up early.

When surgery is advised, the usual aim before the menopause is to keep the ovary. Both Cleveland Clinic and the RCOG describe removing only the cyst (cystectomy) in most cases. Removing the whole ovary is less common and may be considered if the cyst is very large, has replaced the ovary, has twisted and cut off the blood supply, or, rarely, if cancer is suspected.

Keyhole surgery (laparoscopy) is the usual approach. The RCOG notes it tends to mean less pain afterwards and a faster recovery. Open surgery (laparotomy) may be needed for very large cysts or when cancer is a concern. Cleveland Clinic reports that dermoid cysts come back after removal in 3% to 4% of cases.

Dermoid cysts are often first seen on a pregnancy scan. Cleveland Clinic describes them as the most common ovarian tumour found in pregnancy. The RCOG says large or complex cysts may need further scans during pregnancy and after birth, and that surgery in pregnancy is usually reserved for cyst-related pain or, very rarely, suspected cancer.

Every pregnancy is different, so the maternity and gynaecology teams will explain what monitoring they suggest. Tell them straight away about new pelvic pain or bleeding.

Bring the written scan report and any earlier scans so changes in size can be compared.

• How sure are you that this is a dermoid cyst, and what features on the scan point to that?
• What size is it, is it on one or both ovaries, and how does that change the risk of torsion?
• Do you recommend surgery or monitoring for me, and why?
• If surgery is needed, can the ovary be kept, and will it be keyhole surgery?
• If we are monitoring, when is the next scan and who arranges it?
• How might this affect my fertility or a future pregnancy?
• Which symptoms should make me seek urgent care before the next appointment?

On SameCase, patients and verified doctors share de-identified cases. Reading how others with a dermoid cyst of similar size discussed surgery or monitoring with their teams can help you notice questions you had not thought of, such as how follow-up scans were timed or what recovery was like.

Other people's cases cannot tell you what your cyst is or what you should do. Use them to prepare for your appointment, and rely on your own care team for decisions.