An epidermoid cyst is a common, noncancerous lump that develops just beneath the surface of the skin. Although these cysts are usually harmless and slow-growing, they can sometimes become inflamed or infected, requiring medical attention.
Understanding what they look like and how they’re treated can help you decide when to leave them alone and when to see a healthcare provider.
What Is an Epidermoid Cyst?
An epidermoid cyst is a small sac that forms under the skin and fills with keratin — a soft, protein-based material found in skin cells. These cysts develop from the upper part of a hair follicle and are enclosed in a thin wall of skin-like tissue.
They are sometimes mistakenly called “sebaceous cysts,” but they do not involve oil glands and do not contain sebum.
Who Gets Epidermoid Cysts?
Epidermoid cysts are most common in:
Young to middle-aged adults
Men (slightly more often than women)
Individuals with certain genetic conditions
People with long-term sun damage
Those who have experienced skin injury
While anyone can develop one, they are rarely seen in early childhood unless linked to a genetic condition.
What Causes an Epidermoid Cyst?
These cysts usually form when a hair follicle becomes blocked. Instead of shedding normally, skin cells move deeper into the skin and multiply, forming a sac that traps keratin inside.In areas without hair follicles — such as the palms or soles — cysts may develop after skin trauma pushes surface cells into deeper layers.
What Does an Epidermoid Cyst Look Like?
Typical features include:
A round, dome-shaped lump under the skinFlesh-colored, white, or slightly yellow appearance
Size ranging from about 1 to 3 centimeters
A small dark opening (central punctum) on the surface
Thick, cheese-like material that may drain if squeezed
They are most often found on the:Face
Neck
Chest
Upper back
Shoulders
Genital area
Most cysts are painless unless irritated or infected.
Possible Complications
1. Rupture
If the cyst bursts under the skin, it can cause redness, swelling, and tenderness.
2. Infection
Bacteria can enter the cyst, leading to pain, warmth, and pus formation.
3. Recurrence
If not completely removed, the cyst may return.
4. Rare Cancer Risk
In very rare cases, skin cancer can develop within a cyst.
How Is It Diagnosed?
Doctors usually diagnose epidermoid cysts through a physical examination. In most cases, additional testing is not required.If the cyst is removed, the tissue may be sent for laboratory examination to confirm the diagnosis and rule out other conditions.
Conditions That Can Look Similar
Other skin lumps that may resemble an epidermoid cyst include:
Lipomas (soft fatty growths)
Pilar cysts (commonly on the scalp)
Acne-related nodules
Dermoid cysts
Certain viral-related growths
A healthcare provider can determine the difference through examination.
Treatment Options
No Treatment
Small, painless cysts often do not require treatment.
Surgical Removal
The most effective treatment is complete surgical excision, ensuring the entire cyst wall is removed to prevent recurrence.
Drainage
If infected, the cyst may need to be drained and treated with antibiotics.It’s important not to squeeze or attempt to remove a cyst at home, as this increases infection risk.
What Is the Outlook?
Epidermoid cysts are usually benign and slow-growing. Many remain stable for years without causing problems.However, if you notice rapid growth, persistent pain, repeated infections, or changes in appearance, seek medical advice.
When to See a Doctor
Consult a healthcare provider if:
The cyst becomes painful or redIt grows quickly
It repeatedly drains or becomes infected
It interferes with daily activities
You’re unsure whether it’s a cyst
Final Thoughts
Epidermoid cysts are common and typically harmless skin growths. While most do not require treatment, proper medical evaluation ensures accurate diagnosis and prevents complications.If you notice any unusual skin lump, especially one that changes over time, it’s always best to have it checked by a healthcare professional.