Most Common Scalp Cysts
Epidermoid cysts (also called epidermal inclusion cysts) and trichilemmal cysts (pilar cysts) are the two most common cysts on the scalp, with trichilemmal cysts showing particular predilection for the scalp location.
Primary Cyst Types
The scalp is uniquely prone to specific cyst types based on anatomical characteristics:
Trichilemmal (Pilar) Cysts
- Account for approximately 74-96% of all scalp cysts 1, 2
- Show overwhelming scalp predominance—approximately 90% occur on the scalp 3
- More common in females
- Peak incidence in the third decade of life 2
- Can be multiple in presentation, particularly in older patients 4
Epidermoid (Epidermal Inclusion) Cysts
- Most common cutaneous cyst overall (74.3% of all skin cysts), but less scalp-specific 1
- When occurring on the scalp, represent 34% of head and neck cyst locations 2
- Often misidentified as "sebaceous cysts"—this terminology is incorrect 5
- Contain cheesy keratinous material with normal skin flora even when uninflamed 5
Dermoid Cysts
- Third most common type (6.3-22% of cases) 1, 2
- More common in pediatric populations, peaking in the first decade 2, 6
- When on the scalp, can erode through bone (21.94% show partial thickness erosion, 12.23% full thickness) 7
Clinical Differentiation
The key distinguishing feature is location specificity: if the cyst is on the scalp, trichilemmal cyst is statistically most likely; if elsewhere on the head/neck, epidermoid cyst predominates 2.
Important Clinical Pitfalls
Do not assume all scalp cysts are benign—while rare, malignant transformation can occur, particularly in proliferating trichilemmal tumors (2% of trichilemmal cysts) which show local aggression and require careful differentiation 3.
Inflammation does not equal infection: When epidermoid cysts become inflamed and purulent, this typically represents a reaction to cyst wall rupture and extrusion of contents into the dermis, not true bacterial infection 5. Cultures yield normal skin flora, and antibiotics are rarely necessary unless extensive cellulitis, multiple lesions, or systemic symptoms are present.
Risk Factors for Complications
Age and comorbidities influence cyst behavior 4:
- Older patients develop larger and multiple lesions
- Diabetes mellitus independently predicts larger lesions and trends toward higher infection risk
- Hypertension shows negative association with lesion size but may increase infection risk
Management Implications
Surgical excision with complete cyst wall removal is curative 5. For scalp cysts in children, early excision is recommended to prevent bone erosion complications, which is safe even in young patients 7, 6. Simple drainage without wall removal leads to recurrence.