An epidermal inclusion cyst (sebaceous cyst) is a fluid-filled lump under your skin. A keratin substance fills this cyst. It usually doesn’t cause symptoms. Don’t try to pop or remove an epidermal inclusion cyst. A healthcare provider will offer treatment to remove it if it causes discomfort.
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Overview
What is an epidermal inclusion cyst (sebaceous cyst)?
An epidermal inclusion cyst (epidermoid cyst) is a fluid-filled pocket under the surface of your skin. It looks and feels like a lump or bump on your skin.
Many people call epidermal inclusion cysts “sebaceous cysts.” The term “sebaceous cyst” is misleading because the cyst isn’t filled with sebum. Sebum is an oily substance created by your sebaceous glands that keeps your skin moist. Instead, a keratin (protein) and cell debris substance fill epidermal inclusion cysts.
Most healthcare providers only use the term “sebaceous cysts” when associated with the skin condition known as steatocystoma multiplex. Cysts that form with this condition fill with sebum, so they’re truly “sebaceous cysts.” True sebaceous cysts aren’t common, but epidermal inclusion cysts are.
As the name implies, epidermal inclusion cysts form under the top layer of your skin (epidermis).
How common are epidermal inclusion cysts (sebaceous cysts)?
Epidermal inclusion cysts are the most common type of skin cyst.
Symptoms and Causes
What does an epidermal inclusion cyst (sebaceous cyst) look like?
An epidermal inclusion cyst may have the following features:
A round bump or dome-shaped lump.
A dark dot (punctum) in the center of the cyst.
The size ranges from .25 inches to greater than 2 inches. It can grow slowly.
Skin discoloration (usually pink to red or darker than your natural skin tone).
Tender or warm to the touch.
It can move easily.
What are epidermal inclusion cysts (sebaceous cysts) filled with?
A keratin and cell debris substance fills epidermal inclusion cysts. When drained by a dermatologist, this substance looks thick and yellow and has a foul odor.
Is an epidermal inclusion cyst (sebaceous cyst) painful?
An epidermal inclusion cyst isn’t usually painful (asymptomatic). Sometimes, the cyst can inflame (swell) and feel tender when you touch it. As the cyst grows, you may experience skin irritation and pain if it ruptures (breaks open). Occasionally you’ll experience itching at the site of an epidermal inclusion cyst. See your healthcare provider if you develop pain on or near a cyst or have other concerning symptoms.
Where do epidermal inclusion cysts (sebaceous cysts) form?
Epidermal inclusion cysts can form anywhere on your body, but they’re most common on your:
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- Face.
- Chest.
- Back.
- Scalp
- Neck.
- Legs.
- Arms.
- Genitalia.
What causes an epidermal inclusion cyst (sebaceous cyst)?
Epidermal inclusion cysts form after a blockage to a hair follicle (an opening in your skin where hair grows out) at the follicular infundibulum (the top part of the hair follicle).
Your body naturally sheds skin cells when they reach the end of their life cycle. If you have a skin injury like a scratch, surgical wound or a skin condition like acne or chronic sun damage, it can disrupt the path your skin cells take to leave your body. This traps these cells and other components like keratin, so they collect under the surface of your skin. This is how a cyst forms.
On areas of your body where you don’t have hair follicles, a cyst can form after an injury or trauma to your skin, too. The injury pushes your skin cells below the top layer of your skin into the second layer (dermis). This creates a pocket where keratin collects and forms a cyst.
What are the risk factors for epidermal inclusion cysts (sebaceous cysts)?
Although they can appear at any age, epidermal inclusion cysts most frequently occur between ages 20 to 60. Epidermal inclusion cysts rarely appear before puberty. They’re more common among people assigned male at birth (AMAB) than people assigned female at birth (AFAB).
Some rare genetic conditions and other conditions lead to the development of multiple epidermal inclusion cysts:
Gardner syndrome (familial adenomatous polyposis).
Gorlin syndrome (basal cell nevus syndrome).Favre-Racouchot syndrome.Human papillomavirus (HPV).
Certain medications may increase your risk of developing epidermal inclusion cysts, including:
BRAF inhibitors.
Imiquimod.
Cyclosporine.
