Epidermoid (Sebaceous) Cyst

What is an epidermoid cyst?

An epidermoid cyst is a benign cyst that develops within the skin and is lined by cells similar to those in the outer layer of the skin. The cavity gradually fills with keratin, a protein normally found in skin, hair and nails.

These cysts are often called “sebaceous cysts”, but this term is not technically accurate because most do not arise from sebaceous glands.

Epidermoid cysts can occur on many parts of the body and are commonly seen on the face, neck, trunk and back. A related type called a pilar cyst occurs particularly on the scalp.

What does an epidermoid cyst look and feel like?

A typical epidermoid cyst is a rounded lump just beneath the skin. It may be firm or slightly fluctuant and often grows slowly.

A small central opening or punctum may sometimes be visible.

Some cysts remain unchanged for years. Others gradually enlarge. The contents are usually thick keratinous material rather than ordinary liquid. If the cyst opens or is squeezed, this material may have a characteristic unpleasant smell.

An uncomplicated cyst is usually painless.

Why does a cyst suddenly become painful and red?

A cyst may become inflamed if its wall ruptures and keratin escapes into the surrounding tissues. This can produce significant redness, swelling and tenderness even when there is no true bacterial infection.

A cyst can also become secondarily infected.

Distinguishing sterile inflammation from bacterial infection is important because antibiotics are not automatically required for every red or tender cyst.

A very inflamed or infected cyst may occasionally form an abscess and require drainage.

Does every epidermoid cyst need treatment?

No.

A small, typical cyst that is not painful, growing or causing difficulty can usually be observed.

Treatment may be considered when the cyst:

• repeatedly becomes inflamed or infected;
• is painful or tender;
• is gradually enlarging;
• interferes with clothing, shaving or daily activity;
• is cosmetically troublesome;
• discharges repeatedly;
• has recurred after previous drainage; or
• has features that make the diagnosis uncertain.

Any unexplained or unusual lump should be clinically assessed rather than assumed to be a cyst.

What is the definitive treatment?

When definitive treatment is required, complete surgical excision of the cyst together with its wall or capsule is usually preferred.

The procedure is commonly performed under local anaesthesia for small superficial cysts.

An incision is made over the cyst and the cyst wall is carefully separated from the surrounding tissues. Removing the entire cyst lining reduces the risk of recurrence.

If a cyst has previously ruptured or has been repeatedly inflamed, the wall may be adherent to surrounding tissues and complete removal can be more difficult.

What happens if the cyst is acutely infected or very inflamed?

Immediate complete excision is not always the best option when a cyst is acutely inflamed, infected or surrounded by significant swelling.

Depending on the clinical findings, initial treatment may include drainage of an abscess, wound care and antibiotics when bacterial infection or cellulitis is present.

Definitive excision may then be performed later after inflammation has settled.

Simple drainage relieves pressure and infection but does not necessarily remove the cyst lining. The cyst can therefore return after drainage alone.

Can I squeeze or puncture the cyst myself?

This is not recommended.

Squeezing may rupture the cyst wall beneath the skin, causing additional inflammation. It may also introduce infection.

Even if the contents are emptied, the cyst lining usually remains and can refill.

Will there be a scar after removal?

Yes.

Complete surgical removal requires an incision and therefore leaves a scar. The incision is planned according to the size and position of the cyst, skin tension lines and the need to remove the cyst safely.

Previously infected, ruptured or recurrent cysts can sometimes require a larger incision than a small uncomplicated cyst.

Can the cyst come back after surgery?

Recurrence is uncommon when an ordinary epidermoid cyst is completely excised with its lining.

Recurrence is more likely if part of the cyst wall remains, particularly after rupture, previous drainage or difficult dissection.

A recurrent or unusual lump should be reassessed rather than repeatedly drained without confirming the diagnosis.

Is an epidermoid cyst cancerous?

Ordinary epidermoid cysts are benign.

Malignant change within an epidermoid cyst is exceptionally uncommon. More importantly, not every lump that resembles a cyst is necessarily an epidermoid cyst.

A rapidly enlarging, firm, fixed, ulcerated, recurrent or otherwise unusual lesion deserves proper evaluation and sometimes histopathological examination.

What happens after removal?

Most uncomplicated superficial cyst excisions are day-care procedures.

Patients are usually able to go home soon after surgery. The wound should be kept clean and dressed according to the instructions provided.

Activity that pulls significantly on the wound may need to be limited temporarily.

Non-absorbable sutures, when used, are removed according to the site and wound healing.

Removed tissue may be sent for histopathological examination, particularly when confirmation of the diagnosis is appropriate.

When should medical attention be sought?

Seek assessment if a lump is rapidly enlarging, persistently painful, repeatedly inflamed, draining, unusually hard or fixed, or if the diagnosis is uncertain.

After surgery or drainage, increasing redness, swelling, pus, fever, worsening pain, significant bleeding or deterioration should prompt medical review.

This information is intended for general patient education and does not replace individual clinical assessment.