Ultrasound Findings of Dermoid Cysts
Dermoid cysts on ultrasound demonstrate characteristic features including hyperechoic components with acoustic shadowing, hyperechoic lines and dots representing hair, and fluid-fluid levels with floating liquid fat. 1, 2
Key Ultrasound Features
Dermoid cysts (also called mature cystic teratomas) have several distinctive ultrasound appearances:
- Hyperechoic component with acoustic shadowing - Represents calcified material, teeth, or bone within the cyst 1
- Hyperechoic lines and dots - Reflects coiled hair within the dermoid cyst 1
- Fluid-fluid level - Shows nondependent hyperechogenicity consistent with floating liquid fat 1
- Floating echogenic spherical structures - Pathognomonic but less common finding 1
- "Tip of the iceberg" sign - Where only the superficial portion of a highly echogenic lesion is visible due to strong posterior acoustic shadowing 3
- Dermoid mesh - Fine echogenic lines crossing the cyst cavity 3
Variability in Ultrasound Appearance
Despite these "classic" findings, dermoid cysts can present with variable appearances:
- 33% demonstrate the "typical" findings described above
- 23.5% appear predominantly solid
- 20% appear almost entirely cystic
- 23.5% may not be clearly visible on ultrasound 4
This variability highlights the importance of recognizing the spectrum of possible appearances rather than relying on a single "typical" pattern.
Diagnostic Accuracy
Ultrasound has high accuracy for diagnosing dermoid cysts:
- A 1997 study found that 95% of dermoid tumors were correctly characterized by ultrasonography 1
- The presence of two or more characteristic features allows confident diagnosis 3
Differential Diagnosis Considerations
When evaluating a suspected dermoid cyst, consider:
- Endometriomas - Appear as complex unilocular or multilocular cysts with diffuse low-level internal echoes 1
- Hemorrhagic cysts - May contain hypoechoic internal debris or retracting clots 1
- Mucinous cystadenomas - Simple cysts or cysts with thin septations and low-level internal echoes 1
Management Based on Ultrasound Findings
For dermoid cysts <10 cm:
- Annual ultrasound surveillance may be appropriate, especially if asymptomatic 2
- If changing morphology or developing vascular components are observed, referral for MRI is recommended 1, 2
For dermoid cysts ≥10 cm:
- Surgical excision is recommended due to increased risk of complications 2
Pitfalls to Avoid
- Dermoid cysts filled with fat may be confused with pelvic fat tissue 5
- MRI may be needed when ultrasound findings are equivocal 5
- Malignant transformation occurs in 1-2% of cases, most commonly in postmenopausal women 2
- Changes in morphology or development of vascular components warrant further investigation 1
Recognizing these characteristic ultrasound features allows for accurate diagnosis of dermoid cysts and appropriate management decisions based on size, symptoms, and risk factors.