Dermal Cysts: Definition, Types, and Management
A dermal cyst is a benign, closed sac-like structure within the skin that contains keratin and other materials, with epidermoid cysts (often erroneously called sebaceous cysts) being the most common type that typically form from trapped epithelial cells in the dermis or deeper skin tissues. 1
Types and Characteristics
- Epidermoid cysts (commonly mislabeled as "sebaceous cysts") contain cheesy keratinous material and normal skin flora even when uninflamed 1
- Dermoid cysts are congenital choristomas that may contain more complex structures like hair, teeth, and cartilage due to their developmental origin 2
- Cysts can form due to various causes including genetic problems, embryonic development errors, chronic inflammation, blockages of ducts, or injuries 3
Clinical Presentation
- Most dermal cysts present as asymptomatic nodules unless complicated by rupture or infection 1, 4
- When inflamed, epidermoid cysts can present as painful, tender swellings that may mimic abscesses 1
- Cysts typically have a characteristic appearance on imaging:
- Dermoid cysts show hyperechoic components with acoustic shadowing, hyperechoic lines and dots, and sometimes fluid-fluid levels on ultrasound 1, 2
- Epidermal inclusion cysts appear as oval-shaped hypoechoic subcutaneous masses with dermal attachment and intralesional echogenic reflectors on ultrasound 5
Pathophysiology
- Inflammation and purulence in epidermoid cysts typically occur as a reaction to rupture of the cyst wall and extrusion of contents into the dermis, rather than as a primary infectious process 1
- Cysts have a common structure including an outer wall that encapsulates differentiated layers and keratin material 3
- Epidermal inclusion cysts specifically result from dermal or subdermal implantation and proliferation of epidermal squamous epithelium, often following trauma or surgery 4
Management
- For most uncomplicated dermal cysts, the definitive treatment is complete surgical excision to prevent recurrence 6
- For inflamed epidermoid cysts, effective treatment involves:
- Incision and thorough evacuation of the contents
- Probing the cavity to break up loculations
- Covering the surgical site with a dry dressing 1
- Systemic antibiotics are rarely necessary for inflamed cysts unless there are complicating factors such as:
- Multiple lesions
- Cutaneous gangrene
- Severely impaired host defenses
- Extensive surrounding cellulitis
- Severe systemic manifestations of infection (high fever) 1
Special Considerations
- Giant cysts (>4cm) may cause discomfort and require surgical intervention, especially in areas like the axilla 5
- Ruptured cysts can sometimes mimic more serious conditions including malignancies, requiring careful evaluation 4
- Dermoid cysts in specific locations (like ovaries) require specialized management approaches and monitoring, especially in postmenopausal patients due to increased risk of malignant transformation 1, 2