Dermoid cyst (mature cystic teratoma) is a benign ovarian tumor arising from all three germ cell layers (ectoderm, mesoderm, endoderm) and the most common ovarian germ cell neoplasm. Accounts for 10-20% of all ovarian tumors and is most common in premenopausal women (age 20-40). Contents may include fat (sebum), hair, teeth, bone, and skin tissue. Characterized on ultrasound by hyperechoic component due to fat content, Rokitansky nodule (dermoid plug), fat-fluid level, and calcification (teeth/bone). Signal loss on fat-saturated MRI sequences confirms diagnosis. Bilateral in 10-15% of cases. Risk of malignant transformation is <2% (usually >10 cm and >50 years).
Age Range
10-40
Peak Age
25
Gender
Female predominant
Prevalence
Common
Dermoid cyst results from abnormal differentiation of totipotent germ cells. Contains tissue from all three embryonal germ layers: ectoderm (skin, hair, sebaceous glands, neural tissue), mesoderm (fat, muscle, bone, cartilage), and endoderm (thyroid, gastrointestinal epithelium). The majority of cyst content is sebum (fat) — this is the reason for hyperechoic appearance on ultrasound and negative density (-20 to -130 HU) on CT. On MRI, fat shows short T1 relaxation producing bright T1 signal; signal drops on fat-saturated sequences — this 'chemical shift' effect is because fat protons resonate at different frequency. Rokitansky nodule (dermoid plug) is a solid protrusion from the cyst wall containing ectodermal structures like hair, teeth, and bone. The 'tip of the iceberg' sign results from fat content strongly reflecting sound waves and acoustic shadowing of deeper structures — high reflectivity prevents deep penetration.
The combination of fat-fluid level within the cyst (hyperechoic fat above, hypoechoic serous fluid below) and Rokitansky nodule (dermoid plug) protruding from wall into lumen is the most diagnostic imaging finding of dermoid cyst. The coexistence of these two findings is not seen in any other ovarian lesion and confirms diagnosis. Fat-fluid level changes with patient position — fat is superior when patient sits, anterior when supine.
Hyperechoic (bright) fat component within the cyst. Fat as sebum (liquid lipid) constitutes the majority of cyst contents. Hyperechoic area may be punctate or homogeneous.
Report Sentence
A hyperechoic area consistent with fat component is observed within the ovarian cyst, suggesting dermoid cyst (mature cystic teratoma).
Solid, hyperechoic nodular component protruding from cyst wall into lumen (dermoid plug). May contain hair, teeth, or bone tissue. May show posterior acoustic shadowing (calcified content).
Report Sentence
A Rokitansky nodule (dermoid plug) protruding from the cyst wall into the lumen is observed, supporting the diagnosis of dermoid cyst.
Strong echo reflection from the cyst surface and complete shadowing of deeper structures. Cyst depth cannot be assessed due to high reflectivity of fat and hair component — only the 'tip of the iceberg' is visible.
Report Sentence
Superficial hyperechoic reflection with posterior acoustic shadowing is observed in the adnexal region; the 'tip of the iceberg' sign suggests dermoid cyst.
Fat density (-20 to -130 HU) within cyst on CT. Fat-fluid level may be visible. Calcification (teeth, bone) may accompany. Fat density in an ovarian lesion is pathognomonic.
Report Sentence
A cystic lesion containing fat-density (___ HU) component and calcification is seen in the adnexal region, consistent with dermoid cyst (mature cystic teratoma).
Hyperintense (bright) signal on T1-weighted sequences — direct MR evidence of fat content. Signal is isointense to subcutaneous fat.
Report Sentence
The lesion shows hyperintense signal isointense to subcutaneous fat on T1-weighted sequences, suggesting fat content.
Signal loss of T1 bright area on fat-saturated sequence. India ink artifact visible at fat-fluid interface. Definitively confirms fat presence.
Report Sentence
The T1 hyperintense component of the lesion shows signal loss on fat-saturated sequence, definitively confirming macroscopic fat content; consistent with dermoid cyst diagnosis.
High-density (>100 HU) calcification within cyst or Rokitansky nodule — teeth or bone structure. Dental structures may show distinct form (molar/premolar).
Report Sentence
High-density calcification consistent with teeth/bone structure is observed within the cyst, confirming dermoid cyst diagnosis.
Criteria
Majority of cyst content is fat (sebum). Fat-fluid level prominent. Negative density on CT. T1 bright on MRI, dropout on fat-sat.
Distinct Features
Most common type. Diagnosis is straightforward — fat detection establishes diagnosis. Rokitansky nodule and calcification may accompany.
Criteria
Prominent solid component within cyst (large or multiple Rokitansky nodules). Fat component may be minimal. Fat foci within solid component on CT/MRI establish diagnosis.
Distinct Features
May be confused with malignancy due to solid component. However, detection of fat foci or calcification even within solid area favors dermoid. If malignant transformation suspected (>10 cm, >50 years, increased enhancement), surgery recommended.
Criteria
Dermoid cyst in both ovaries. Seen in 10-15% of cases. Contralateral ovary must always be evaluated.
Distinct Features
Detection of fat content in both lesions establishes bilateral dermoid diagnosis. Krukenberg metastasis and bilateral cystadenoma should be considered in differential of bilateral cystic ovarian lesions — fat presence favors dermoid.
Distinguishing Feature
Endometrioma may be T1 bright (blood products) but does not show signal loss on fat-saturated sequence (methemoglobin preserves signal). Dermoid is T1 bright and loses signal on fat-sat (fat). T2 shading is pathognomonic in endometrioma, absent in dermoid.
Distinguishing Feature
Hemorrhagic cyst is T1 bright (methemoglobin) but does not lose signal on fat-sat. Dermoid is T1 bright and loses signal on fat-sat. On CT, hemorrhagic cyst shows positive density (40-70 HU), dermoid shows negative density (-20 to -130 HU).
Distinguishing Feature
Mucinous carcinoma shows multilocular, septated cystic compartments with different densities. No fat density (positive density on CT). No signal loss on fat-sat MRI. Solid enhancing components and papillary projections suggest malignancy. Fat + calcification combination in dermoid is diagnostic.
Urgency
routineManagement
surgicalBiopsy
Not NeededFollow-up
annualDermoid cyst is a benign tumor but does not show spontaneous regression — surgical resection (cystectomy or oophorectomy) is standard treatment. Annual US follow-up is acceptable for small (<5 cm), asymptomatic dermoids. Surgery is planned for >5 cm or symptomatic (pain, pressure) lesions. Torsion risk increases with size — cysts >6-8 cm have high torsion risk and prophylactic surgery is considered. Malignant transformation (usually squamous cell carcinoma) risk is <2% with >10 cm size and >50 years as risk factors. Cyst rupture may cause chemical peritonitis — requires emergency intervention. Cystectomy is preferred for bilateral dermoid to preserve ovarian function.
Dermoid cysts are generally benign with 1-2% risk of malignant transformation (usually squamous cell carcinoma). Torsion risk exists (16%). Rupture is rare but can cause chemical peritonitis. May be bilateral (10-15%).