Mature cystic teratomas are cystic tumors composed of well-differentiated derivations from at least two of the three germ cell layers (ectoderm, mesoderm, and endoderm). They affect a younger age group (mean patient age, 30 years) than epithelial ovarian neoplasms. Mature cystic teratoma is the most common germ cell neoplasm and, in some series, the most common ovarian neoplasm. The tumors are bilateral in about 10% of cases. Most mature cystic teratomas are asymptomatic. Complications include rupture, malignant degeneration, or (most commonly) ovarian torsion.

• Most mature cystic teratomas can be diagnosed at US.
• The most common manifestation is a cystic lesion with a densely echogenic tubercle (Rokitansky nodule) projecting into the cyst lumen.
• The second manifestation is a diffusely or partially echogenic mass with the echogenic area usually demonstrating sound attenuation owing to sebaceous material and hair within the cyst cavity.
• The third manifestation consists of multiple thin, echogenic bands caused by hair in the cyst cavity.
• The diagnosis of mature cystic teratoma at CT and MR imaging is fairly straightforward because these modalities are more sensitive for fat than US.

Patient #1: US and MR images demonstrate a large dermoid

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  T1
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  T1
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  T2
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  T2
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  T2
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  T1 fat sat
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  T1 fat sat post contrast
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  T1 fat sat post contrast

Patient #2: CT images demonstrate left ovarian mature cystic teratoma