Definition
- Benign encapsulated subepidermal cyst filled with keratin and lined by stratified squamous epithelium
- Also known as Epidermoid cyst and Epidermal Inclusion Cyst
- Sebaceous cyst is a misnomer because the cyst is not filled with sebum nor do they arise from sebaceous glands.
Incidence
- Early adulthood, M > F 2:1
- Patients with Gardner syndrome develop lots of lesions
Aetiology
- Occlude pilosebaceous unit
- Creates a cyst filled with keratin and lipid-rich debris
- Causes
- Congenital: Implantation during embryology
- Traumatic / surgical implantation
- Epidermal inclusion cyst where skin is ‘tucked in’ then continues to produce keratin which becomes trapped
- Occlusion of the pilo-sebaceous unit
Pathophysiology
- Blockage of the hair follicle then accumulation of keratin
- Rupture
- Incites an inflammatory reaction (? in response to trapped keratin)
- ± Secondary infection
- Smooth dome shaped fixed to under surface of epidermis ± punctum
- Face, scalp, neck & trunk
- Lined with keratinised squamous epithelium & granular cell layer, filled with keratin
- Multiple lesions associated with Gardner’s Syndrome (variant of FAP)
