Dermoid cyst of the ovary: what it is, symptoms and treatment

An ovarian cyst is a fluid-filled sac that develops on an ovary, and the NHS describes them as very common. A dermoid cyst is a particular type that does not form as part of the menstrual cycle. The ISUOG patient leaflet says ovarian dermoid cysts, medically called mature cystic teratomas, are benign ovarian masses arising from germ cells.

The name dermoid reflects the fact that the cyst can contain skin-like material. The ISUOG leaflet gives a broader list: hair, sweat glands, teeth and brain tissue, muscle fibres, cartilage, bone and fatty tissue, and thyroid, respiratory and gastrointestinal tissue. It explains that genetic studies show these cysts grow from a single unfertilised egg cell, which divides and can turn into many kinds of cell.

This unusual make-up is why a dermoid is described as a mass of mixed tissue rather than a simple fluid-filled sac.

Many dermoid cysts cause no symptoms and are discovered during a scan for another reason. The ISUOG leaflet states that they can cause pelvic discomfort because of mass effects, torsion or cyst rupture. The NHS page on ovarian cysts more generally says a cyst usually causes symptoms only if it splits, is very large or twists and blocks the blood supply to the ovary.

The NHS lists symptoms of ovarian cysts that include pelvic pain ranging from a dull, heavy sensation to a sudden, severe and sharp pain, pain during sex, difficulty emptying the bowels, a frequent need to urinate, changes to periods, bloating and a swollen tummy, and feeling very full after eating only a little. These are not specific to dermoid cysts, and many other conditions can cause them.

The NHS says to see a GP if you have symptoms of an ovarian cyst, and to ask for an urgent GP appointment or get help from NHS 111 if you have sudden, severe pelvic pain, or pain in the tummy together with feeling sick or being sick.

If a GP thinks you may have an ovarian cyst, the NHS says you will probably be referred for an ultrasound scan, usually with a probe placed inside the vagina. If a cyst is found it may be monitored with a repeat scan in a few weeks, or you may be referred to a gynaecologist. The NHS adds that if there is concern that a cyst could be cancerous, blood tests may be arranged, although raised levels of the chemicals measured can also occur with non-cancerous conditions such as endometriosis, a pelvic infection, fibroids or a period.

The ISUOG leaflet stresses that, although dermoid cysts are almost always benign, clinical and ultrasound evaluation are important for a correct diagnosis and during follow-up. It says follow-up is performed to monitor growth and to detect signs of malignant transformation, and it describes malignant transformation as very rare.

ISUOG also notes that in some extremely rare cases certain blood and neurological diseases can occur because of substances released into the bloodstream by ovarian teratomas. This is mentioned as a rare possibility, not as a usual feature.

Twisting of the ovary and cyst on its supporting tissue is called torsion. The NHS ovarian cyst page lists twisting that blocks the blood supply to the ovary among the situations in which a cyst causes symptoms, and sudden severe pelvic pain is the warning sign it highlights. Rupture, where the cyst splits, can also cause sudden pain.

ISUOG says the risks of rupture and torsion rise as a dermoid cyst increases in size. That is one reason size is an important part of deciding between follow-up and removal. It also notes that spillage of cyst contents at surgery can result in a painful inflammation of the inner lining of the abdomen, which is a reason surgeons take care during removal.

There is not a single approach for everyone. ISUOG says that for children and women of childbearing age with no discomfort, watchful waiting is a safe and good option. If the person experiences discomfort or feels insecure, the gynaecologist can opt to remove the cyst while sparing the surrounding normal ovarian tissue.

In some situations removal of the whole ovary with the tube may be more appropriate, for example in older patients or if the cyst is very large. The NHS makes a similar point about fertility on its ovarian cyst page: surgeons aim to preserve fertility whenever possible, which may mean removing just the cyst and leaving the ovaries intact, and it recommends discussing the potential effects on fertility before an operation.

ISUOG says recurrence after surgery has been documented in up to 7.6% of cases. It lists useful questions to ask the doctor, including whether the cyst can be followed up, what warning signs to watch for, whether it needs removing, how extensive the surgery will be and what risks an operation brings.

The NHS says ovarian cysts do not usually prevent pregnancy, although they can sometimes make it harder to conceive, and that fertility is usually unaffected. The ISUOG leaflet frames watchful waiting as a reasonable option for women of childbearing age without symptoms, and fertility-sparing surgery as the aim when removal is needed.

The NHS says that most ovarian cysts occur naturally and go away in a few months without treatment, and that the two main types are functional cysts, which develop as part of the menstrual cycle, and pathological cysts, which form from abnormal cell growth. Because the type of cyst shapes the plan, a scan report that names it is worth discussing with the clinician who ordered it.