ConditionSkin, hair & nails
Epidermoid Cyst
An epidermoid cyst is a common, harmless, slow-growing lump just under the skin. It is a sac lined with skin cells that fills with soft, cheesy keratin, often with a small dark opening (punctum) on top. They usually appear on the face, neck, chest, upper back and behind the ears. They are often wrongly called sebaceous cysts. Most need no treatment, but cysts that become red, swollen and painful, or keep returning, can be drained or surgically removed.
Also called: Epidermal cyst, epidermal inclusion cyst, infundibular cyst, "sebaceous cyst" (common but inaccurate)
At a glance
- What it is
- A benign sac under the skin filled with keratin.
- Where
- Face, neck, scalp, chest, back, behind the ears, genitals.
- Typical look
- Round, firm, movable lump, often with a central dark pore.
- Complications
- Inflammation, rupture, infection, and return after drainage.
- Treatment
- Leave alone, steroid injection or drainage when inflamed, surgical removal of the whole sac to prevent return.
When to get help
See a doctor within a day or two
- A cyst that is rapidly becoming red, hot, swollen and very painful, with spreading redness or fever above 38 °C (100.4 °F)
- Red streaks spreading from the cyst
Book a routine appointment
- A painful or inflamed cyst that is not settling after a few days of warm compresses
- A cyst that keeps coming back, is growing quickly, or bothers you
- A lump that is hard, fixed, irregular, bleeding or ulcerated
- Multiple cysts appearing in childhood, especially with a family history of bowel polyps
Usually safe to manage at home
- A small, painless, slow-growing cyst that has been stable
What an epidermoid cyst is
The top layer of skin (epidermis) constantly sheds dead cells. If epidermal cells end up below the surface, usually in a blocked hair follicle opening or after an injury, they form a closed sac. The sac keeps producing keratin, a soft protein, which builds up as a cheesy, white-yellow material with a rancid smell if released.
Epidermoid cysts are not the same as true sebaceous cysts (steatocystomas), which come from oil glands. The name "sebaceous cyst" persists in everyday use.
Symptoms and appearance
- a smooth, round, dome-shaped lump, from a few millimeters to several centimeters across
- firm or doughy, and moves slightly under the skin
- skin-colored, white or yellowish
- a small dark pore (punctum) in the center in many cases
- usually painless unless inflamed
- may slowly enlarge over months to years
Inflamed or ruptured cyst
When the wall leaks, keratin spills into the surrounding skin and triggers strong inflammation. The cyst becomes red, swollen, hot and tender, and may discharge pus-like, foul-smelling material. Much of this is inflammation rather than infection, but bacterial infection can follow.
Causes and risk factors
- blocked hair follicle openings
- acne, particularly in young adults
- skin injury, piercing or surgery (implanting skin cells deeper)
- sun damage
- Gardner syndrome: multiple epidermoid cysts in childhood can be a sign of this inherited condition, which also causes colon polyps. See Gardner syndrome
- Basal cell nevus syndrome and some other genetic conditions
They are most common in adults aged 20 to 50 and somewhat more common in men.
Similar lumps
| Lump | How it differs |
|---|---|
| Pilar cyst | On the scalp, smooth, no punctum, often runs in families |
| Lipoma | Soft, rubbery fat lump, deeper, no punctum |
| Dermoid cyst | Present from birth, often near the eyebrow, contains hair and other structures |
| Milia | Tiny 1 to 2 mm white bumps, often around the eyes |
| Abscess | Fast-growing, very painful pus collection, often from a boil |
| Skin cancer | Firm, growing, irregular, may bleed or ulcerate |
Diagnosis
A doctor usually diagnoses an epidermoid cyst by examining it. An ultrasound helps if the lump is deep or unusual. Removed cysts are often sent to a lab to confirm the diagnosis. Very rarely, cancer arises in a cyst, so unusual features prompt a biopsy.
Treatment
No treatment
Small, painless cysts can be left alone. Do not squeeze them: this can rupture the wall into the skin and cause painful inflammation.
Inflamed cysts
- Warm compresses for 10 to 15 minutes, several times a day, can help it settle or drain.
- Steroid injection into the cyst reduces inflammation quickly.
- Incision and drainage relieves a tense, painful cyst, but the sac remains, so it usually comes back.
- Antibiotics are used only if there is spreading cellulitis or clear infection.
Removal
- Surgical excision: the whole cyst and its wall are removed under local anesthetic, usually once inflammation has settled. This gives the lowest chance of return.
- Minimal excision or punch technique: a small hole is made and the contents and wall are removed through it, leaving a smaller scar, best for non-inflamed cysts.
- Laser techniques in some clinics.
Removing a cyst leaves a scar, so weigh this against how much it bothers you.
Outlook
Epidermoid cysts are benign. They may stay the same for years, slowly grow, or occasionally shrink. Complete surgical removal usually cures them, while drainage alone often leads to recurrence.
Frequently asked questions
What is an epidermoid cyst?
It is a harmless lump under the skin made of a sac of skin cells filled with soft keratin. It is often round and firm with a small dark pore on top, and commonly appears on the face, neck, chest or back.
Should I pop an epidermoid cyst?
No. Squeezing a cyst can rupture its wall under the skin, causing painful inflammation, infection and scarring, and the cyst usually returns. Use warm compresses and see a doctor if it becomes painful or swollen.
Is an epidermoid cyst the same as a sebaceous cyst?
They are often called the same thing, but technically no. Epidermoid cysts come from the skin's surface layer and contain keratin. True sebaceous cysts (steatocystomas) come from oil glands and are less common.
Will an epidermoid cyst go away on its own?
Some shrink, but most persist and may slowly grow. They can drain and seem to disappear, but often refill because the sac is still present. Complete surgical removal of the sac is the only reliable cure.
Can an epidermoid cyst be cancer?
Epidermoid cysts are almost always benign. Cancer arising in one is extremely rare. A lump that is hard, fixed, growing fast, bleeding or ulcerated should be checked, and removed cysts can be sent to a lab for confirmation.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Dermatology: Cysts, diagnosis and treatment
- American Osteopathic College of Dermatology: Epidermoid cyst
- DermNet: Epidermoid cyst
- MedlinePlus (US National Library of Medicine): Sebaceous cyst
- NHS: Sebaceous cysts