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Mature (cystic) ovarian teratoma

Dr Henry Knipe and Dr Frank Gaillard et al.

Ovarian dermoid cyst and mature cystic teratoma are terms often used interchangeably to refer to the most common ovarian neoplasm. These slow-growing tumours contain elements from multiple germ cell layers and are best assessed with ultrasound. 

Terminology

Although they have very similar imaging appearances, the two have a fundamental histological difference: dermoids are composed only of dermal and epidermal elements, whereas teratomas have mesodermal and endodermal elements. 

For the sake of simplicity both are discussed in this article, as much of the literature combines the two entities. 

Epidemiology

Mature cystic teratomas account for ~15% (range 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

Uncomplicated ovarian dermoids tend to be asymptomatic and are often discovered incidentally. They do, however, predispose to ovarian torsion, and may then present with acute pelvic pain. 

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 (i.e. ectoderm, mesoderm, and endoderm). They therefore contain 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, and rarely more than 15 cm. Real organoid structures (teeth, fragments of bone) may be present in ~30% of cases.

Location

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

Variants

Radiographic features

Conventional radiograph

May show calcific and tooth components with the pelvis.

Pelvic ultrasound

Ultrasound is the preferred imaging modality. Typically an ovarian dermoid is seen as a cystic adnexal mass with some mural components.  Most lesions are unilocular.

The spectrum of sonographic features includes:

  • diffusely or partially echogenic mass with posterior sound attenuation owing to sebaceous material and hair within the cyst cavity
  • mural hyperechoic Rokitansky nodule: dermoid plug
  • echogenic, shadowing calcific or dental (tooth) components
  • presence of fluid-fluid levels 5
  • multiple thin, echogenic bands caused by hair in the cyst cavity: the dot-dash pattern
  • colour Doppler: no internal vascularity
    • internal vascularity requires further workup to exclude a malignant lesion
CT

CT has high sensitivity in the diagnosis of cystic teratomas 6 though it is not routinely recommended for this purpose owing to its ionising radiation.

Typically CT images demonstrate fat (areas with very low Hounsfield values), fat-fluid level, calcification (sometimes dentiform), 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 10 cm or soft tissue plugs and cauliflower appearance with irregular borders are seen, malignant transformation should be suspected 5.

When ruptured, the characteristic hypoattenuating fatty fluid can be found as antidependent pockets, typically below the right hemidiaphragm, a pathognomonic finding 2. The escaped cyst content also leads to a chemical peritonitis and the mesentery may be stranded and the peritoneum thickened, which may mimic peritoneal carcinomatosis 2

Pelvic MRI

MR evaluation usually tends 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 the presence of fat. 

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

Treatment and prognosis

Mature ovarian teratomas are slow growing (1-2 mm a year) and, therefore, some advocate nonsurgical management. Larger lesions are often surgically removed. Many recommend annual follow up for lesions <7 cm to monitor growth, beyond which a resection is advised.

Complications

Recognised complications include:

  • ovarian torsion: ~3-16% of ovarian teratomas, in 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)
  • superimposed infection: 1%
  • autoimmune haemolytic anaemia: <1%.

Differential diagnosis

General differential imaging considerations include:

See also


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