Epidermoid and Piloid cysts

Question 1

What are Epidermoid and Piloid cysts?

Answer 1

Sebaceous cysts
Both contain keratin, not sebum + DONT originate from sebaceous glands.
Epidermoid cysts originate in the epidermis
Pilar cysts originate from hair follicles.

Question 2

Describe the aetiology of sebaceous cysts

Answer 2

Occlusion of the pilosebaceous gland
Can be caused by traumatic insertion of epidermal elements into the dermis
Embryonic remnants

Question 3

Describe the epidemiology sebaceous cysts

Answer 3

VERY COMMON at any age
Epidermoid cyst affects young + middle aged adults, + are common in acne
Pilar cysts affect women more + tend to occur in middle age

Question 4

Which syndrome predisposes to sebaceous cyst formation?

Answer 4

Gardner’s Syndrome

AD condition; multiple polyps in the colon + extra-colonic sites (e.g. sebaceous cyst, thyroid cancer, fibroma)

Question 5

How do sebaceous cysts present?

Answer 5

Non-tender slow-growing skin swelling
Often multiple
Common on hair-bearing regions of the body (e.g. face, scalp, trunk or scrotum)

Question 6

How may sebaceous cysts present if infected or inflamed?

Answer 6

Red, hot + tender

Infection is quite common: discharge cheesy foul-smelling pus

Question 7

Describe the appearance of sebaceous cysts

Answer 7

Firm, round, mobile subcutaneous nodules of varying size 
Characteristic overlying central punctum (epidermoid only) 
Foul pus (granular + creamy) exits through the punctum

Question 8

What investigations are performed for sebaceous cysts?

Answer 8

None needed

Question 9

What investigations may be used in suspected sebaceous cysts to exclude differentials?

Answer 9

Skin biopsy

FNA