What is an epidermal cyst (Sebaecous Cyst)

• Cyst attached to skin which may have a punctum from which can be expressed cheesy material.

• Most are found on hair-bearing areas of the body – head, neck, scrotum, trunk, shoulders

What is the origin of epidermal cysts

• Believed to arise from infundibular portion of hair follicle

• Histologically have keratinizing squamous epithelium with a granule cell layer

• Contents: kertain

• Multiple epidermal cysts are associated with Gardner’s syndrome

What is a trichilemmal or pilar cyst

• Clinically indistinguishable from epidermal cyst, but believed to arise from outer root sheath of hair follicle due

•  Differentiated histologically by absence of granule cell layer in their lining.

• Contains desquamated cells rather than keratin.

• 90% occur on the scalp. 

• There is an AD genetic predisposition to trichilemmal cysts in 70% of cases

Are either derived from sebaceous glands

• No

What are the complications

• Infection with abscess formation

• offensive discharge

What is Cock’s Peculiar tumour

• Infected granulating Trichlemmal cyst.

• Almost always on scalp.

• Resembles SCC

What is the treatement

• Excise with an elipse of over-lying skin

What is a dermoid cyst

• A cyst, deep to the skin, lined by skin

• The cyst is lined by stratified squamous epithelium which (unlike sebaceous cyst) has all the other appendages of skin (hair follicles, sweat glands and sebaceous glands.)

What are the types of dermoid

• Congenital and acquired

Where do congenital dermoids form

• Lateral and medial ends of the eyebrow (external and internal angular)

• Midline anteriorly (Midline nose, sublinguinal, midline of neck)

• Any point of midline of trunk (perineum and scarum)

Why are they complicated

• Midline dermoids may penetrate down to the dura especially when found along the cranio-spinal axis.

How are they treated

•  Often best managed conservatively  if asymptomatic.

•  CT scan to assess penetration

What is an acquired dermoid

Survival of a piece of skin forcibly implanted into the subcutaneous tissue

•  may be tethered to skin by scar tissue

•  Most common on the fingers