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Ovarian dermoid cyst

An ovarian dermoid cyst or a mature cystic teratoma is the commonest type of ovarian teratoma. It is also the most common ovarian neoplasm 2.

Epidemiology

Mature cystic teratomas account for 10 - 20% of all ovarian neoplasms. They tend to be identified in young women, typically around the age of 30 years 1 and are also the most common ovarian neoplasm in patients younger than 20 years 8.

Clinical presentation

More lesions tend to be asymptomatic and are discovered incidentally. Patients may present acutely with on of the possible complications liseted further down in the article. 

Pathology

Mature cystic teratomas are encapsulated tumours with mature tissue or organ components. They are composed of well-differentiated derivations from at least two of the three germ cell layers (ectoderm, mesoderm, and endoderm). They therefore contains developmentally mature skin complete with hair follicles and sweat glands, sometimes luxuriant clumps of long hair, and often pockets of sebum, blood, fat, bone, nails, teeth, eyes, cartilage, and thyroid tissue. Typically their diameter is smaller than 10 cm, rarely more than 15 cm. Real organoid structures (teeth, fragments of bone) may be present in ~ 30% of cases.

Location - laterality

They can be bilateral in 10 - 15% of cases 1-2

Variants

Radiographic features

Plain film

May show calcific and tooth components with the pelvis

Pelvic ultrasound

Ultrasound is the preferred investigative imaging modality. Typically ovarian dermoids are seen as a cystic adnexal mass with some mural components.

Sonographic features include

  • presence of a Rokitansky nodule - dermoid plug
  • posterior shadowing from calcific, dental (tooth) components : sometimes decribed as the tip of the iceberg sign
  • presence of fluid-fluid levels 5
  • most lesions are unilocular
  • diffusely or partially echogenic mass with posterior sound attenuation owing to sebaceous material and hair within the cyst cavity
  • multiple thin, echogenic bands caused by hair in the cyst cavity
CT

It has been demonstrated that a CT scan is the best imaging procedure for the diagnosis of cystic teratomas 6.

Typically CT images demonstrate fat (areas with very low Hounsfield values), fat fluid level, calcification (sometimes tooth), Rokitansky protuberance and tufts of hair. The presence of most of the above tissues is diagnostic of ovarian cystic teratomas in 98% of cases 5. Whenever the size exceeds 10cms or soft tissue plugs and cauliflower appearance with irregular borders is seen, malignant transformation should be suspected 5.

Pelvic MRI

MR evaluation usually tends tend to be reserved for difficult cases, but is exquisitely sensitive to fat components. Both fat suppression techniques and chemical shift artefact can be used to confirm presence of fat. 

Enhancement is also able identify solid invasive components, and as such can be used to accurately locally stage malignant variants. 

Complications

Recognised complications include

  • ovarian torsion :  ~ 3 - 16% of ovarian teratomas on general : considered the most common complication
  • rupture : ~ 1 - 4%
  • malignant transformation : ~ 1 - 2% : usually into squamous cell carcinoma (adults) or rarely into endodermal sinus tumours (paediatrics).
  • suprimposed infection : 1%
  • autoimmune haemolytic anaemia :  < 1%.

Treatment and prognosis

They are slow growing (1 - 2 mm a year) and therefore some advocate non surgical management. Larger lesions are often surgically removed. Many recommoned initial serial follow for lesions under 7 cm  to monitor growth beyond which a resection is advised.

Differential diagnosis

Differential considerations include :

See also

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