What is a Dermoid Cyst on an Infant?
A dermoid cyst in an infant is a benign congenital tumor that develops from both ectodermal and mesodermal germ cell layers during embryonic development, appearing as a slow-growing mass that most commonly occurs in the head and neck region and requires complete surgical excision to prevent complications.
Definition and Developmental Origin
A dermoid cyst is a developmental choristoma that forms when epithelial cells become trapped along embryonic fusion lines during fetal development 1, 2. Unlike simple epidermoid cysts, dermoid cysts contain more complex structures derived from multiple germ layers, including:
Approximately 70% of dermoid cysts are discovered in children aged five years or younger, with the majority being congenital 2, 4.
Location and Clinical Presentation
Common Sites in Infants
Head and neck dermoid cysts account for only 7% of all dermoid cysts in the body, yet this is the most common location in the pediatric population 2, 5. Within the head and neck region:
- Cranial locations: Frontonasal (between nasal bone and cartilage) and parieto-occipital regions are most common 3
- Lumbosacral region: Can occur along the spine, often with skin appendages and hair in the ostium 3
- Subcutaneous locations: May present as simple subcutaneous masses 3
Physical Examination Findings
Dermoid cysts typically present as:
- Asymptomatic, slow-growing nodules that can remain stable for years 1, 4
- Painless masses unless complicated by rupture or infection 5
- Sebaceous or creamy fluid that can sometimes be expressed from the ostium 3
- Characteristic appearance with possible hair, skin appendages, or surrounding infantile hemangioma 3
Critical warning signs requiring urgent evaluation include masses that are fixed to adjacent tissues, firm in consistency, >1.5 cm, or have ulceration of overlying skin 6.
Diagnostic Approach
Imaging Studies
MRI is the preferred imaging modality as it can demonstrate characteristic features including fatty and calciferous content that may be pathognomonic for dermoid cysts 3, 6.
Complementary imaging includes:
- CT scanning: Reveals bony defects (such as at the foramen cecum) and intracranial calcifications 3
- Ultrasound: Shows hyperechoic components with acoustic shadowing, hyperechoic lines and dots, and sometimes fluid-fluid levels 6, 1
Critical Imaging Considerations
For frontonasal dermoid cysts, 10-30% extend intracranially through the skull base at the foramen cecum, making pre-operative imaging mandatory 3. Similarly, parieto-occipital dermoid cysts more frequently have intracranial extension through midline occipital skull defects 3.
Imaging should always be performed before surgical intervention when cysts present in the nose, face, or scalp due to the possibility of intracranial connection 7, 4.
Potential Complications
Serious Risks if Untreated
Dermoid cysts can cause significant morbidity through three mechanisms:
Infection risk: Serving as a portal of entry for bacteria, producing meningitis, subdural empyema, or brain abscess 3, 6
Aseptic meningitis: Through desquamation of epithelial debris from the tract and/or associated cysts 3
Mass effect: Causing intracranial hypertension and/or focal brain compression through progressive enlargement 3
When dermoid cysts occur on the floor of the mouth, they may enlarge to such an extent that they interfere with swallowing and produce respiratory obstruction 5.
Growth Pattern
Unlike true tumors that grow exponentially, dermoid cysts exhibit a linear growth pattern in all three dimensions, following a cuboid sequence 8. This slow but persistent growth underscores the importance of early surgical intervention.
Management
Surgical Treatment
Complete surgical excision is the definitive treatment for dermoid cysts in infants to prevent recurrence and potential complications 6, 5. Key surgical principles include:
- Timing: Early diagnosis and treatment are essential to minimize morbidity 5, 4
- Approach: Dictated by the cyst's location and extent of involvement 6, 5
- Extent: Total excision is necessary; incomplete removal leads to recurrence 5, 4
For frontonasal dermoid cysts, treatment should proceed regardless of imaging findings to eliminate the tract and prevent future complications, even though most will involve only local nasal excision 3.
Role of Antibiotics
Antibiotics are rarely necessary for inflamed dermoid cysts unless there are complicating factors such as extensive surrounding cellulitis or severe systemic manifestations of infection 6, 1. The inflammation typically results from rupture of the cyst wall and extrusion of contents into surrounding tissue rather than primary infection 1.
Gram stain and culture of pus from inflamed cysts is not recommended 6.
Follow-Up
Evaluation should continue until a definitive diagnosis is obtained, and clinicians should not assume the mass is benign without histopathological confirmation 6. A documented follow-up plan is essential to assess resolution or obtain final diagnosis 6.
No recurrence has been documented in case series when complete surgical excision is performed 4.
Common Pitfalls to Avoid
- Misdiagnosis: Frontonasal dermoid cysts can be easily overlooked or misdiagnosed as pimples or comedones due to their innocuous appearance 3
- Inadequate pre-operative imaging: Failure to identify intracranial extension before surgery can lead to incomplete resection and serious complications 7, 4
- Confusion with other lesions: Atretic parieto-occipital encephaloceles can be confused with dermoid cysts and require different management 3
- Delayed treatment: Allowing cysts to enlarge increases risk of complications including airway compromise and infection 5, 4