Dermoid Cyst
Synonyms/Description
Mature cystic teratoma
Etiology
This is a benign germ cell tumor containing ectoderm, mesoderm, and endoderm, thought to arise from a single germ cell. Components may include hair, teeth, fat, and bone. These tumors represent 25% of all ovarian neoplasms and 60% of all benign ovarian tumors. They are bilateral and or recurrent in 10% of cases. These lesions are benign and typically occur in teenagers and young adults, although approximately 1% may be immature teratomas with malignant components mixed with mature elements.
Ultrasound Findings
The classic sonographic appearance of a dermoid is an echogenic mass with intense acoustic shadowing obscuring the back wall. A finding coined “tip of the iceberg” refers to this characteristic, which can make obtaining accurate measurements of the mass difficult. The intensely echogenic components of dermoid cysts represent varying combinations of fat, sebaceous material, hair, teeth, and bone. There are often a multitude of thin echogenic lines emanating from the echogenic center representing strands of hair within the mass. The so-called “Rokitansky nodule” is a very echogenic, discrete, rounded protuberance characteristic of a dermoid. There is typically no demonstrable blood flow within these lesions.
Less commonly, dermoids can be predominantly cystic with only a small echogenic nodule that is easy to miss and that indicates the correct diagnosis. There can be septations and low-level echoes, which may be confused as findings consistent with an endometrioma. Occasionally, dermoids can be made up of a multitude of small round balls within a mass, like a cluster of billiard balls. This is rare but when visualized is a characteristic appearance of a dermoid cyst.
Differential Diagnosis
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