Epidermoid Cyst
An epidermoid cyst, also known as a keratin cyst, epidermal cyst, epidermal inclusion cyst, sebaceous cyst, or an epithelial cyst, is a keratin-filled epithelial-lined cyst.
EPIDEMIOLOGY
Epidermoid cysts are found most commonly in adult men and women. Genetic disorders, such as Gorlin syndrome (nevoid basal cell carcinoma syndrome), pachonychia congenita type 2 (Jackson-Lawler type), and Gardner syndrome, may predispose individuals to having this type of cyst.
ETIOLOGY AND PATHOGENESIS
Epidermal cysts are most commonly the result of plugged pilosebaceous units. These cysts express the same cytokeratin profile as the follicular infundibulum. Epidermal cysts can also be caused by the traumatic implantation of epidermal cells into deeper tissues or by the proliferation of viable epidermal remnants along embryonic fusion planes. Epidermoid cysts can be located anywhere on the body and are characterized by their distinctive pathology. Recently, HPV type 57 and 60 DNA has been detected in palmoplantar epidermoid cysts.
CLINICAL PRESENTATION
Epidermoid cysts are classically dermal or subcutaneous mobile nodules with a central punctum . Lesions not associated with trauma are commonly located on the upper chest, upper back, neck, or head. Traumatic lesions are more common on the palms, soles, or buttocks. The punctum, when present, represents the plugged pilosebaceous unit from which cheesy debris may be expressed. These lesions can be skin-colored, yellow, or white. Cysts are usually slow-growing and asymptomatic, though rupture is common