An epidermoid cyst is a sac lined with epidermis, filled with keratin. The contents are not the problem — the wall is.
Book an assessment →A sebaceous cyst is usually an epidermoid cyst: a skin-lined sac under the skin that fills with keratin. Most are harmless, but a cyst refills if only the contents are squeezed out, because the wall stays behind. Lasting removal means taking out the intact wall under local anaesthetic once any inflammation has settled. See skin growths, lumps and bumps.
The cyst wall continuously produces keratin into its own cavity, and a central punctum is often visible. They are commonly, and inaccurately, called sebaceous cysts.
A sebaceous cyst is a smooth, round lump just under the skin that moves slightly with your finger. Most do not hurt and grow slowly. Many have a tiny dark pore in the centre, called a punctum, which is the blocked opening of the hair follicle the cyst came from. If the cyst leaks, the contents are a soft, pale, cheesy material with a strong smell.
The name is misleading. Almost all so-called sebaceous cysts are epidermoid cysts (also called epidermal or epidermal inclusion cysts): a small sac lined with skin, like the surface of the body folded inwards. That lining keeps producing keratin, the protein of the outer skin, and sheds it into the sac. The cheesy material is keratin, not oil. On the scalp, a similar lump is usually a pilar cyst, which has a thicker wall and tends to run in families. A true cyst of the oil glands, called steatocystoma, is uncommon.
They form when skin cells end up below the surface, usually from a blocked follicle, sometimes after an injury or acne, and are common on the face, behind the ears, neck, chest, upper back and scalp.
Several lumps feel similar. The table sets out the usual differences; an examination decides which one you have.
| Lump | How it feels | Clues | Usual approach |
|---|---|---|---|
| Epidermoid (“sebaceous”) cyst | Smooth, firm-to-soft, moves with the skin | Central punctum; cheesy, smelly contents if it leaks | Leave it, or remove the whole sac |
| Lipoma | Soft, rubbery, slides under the skin | Not tied to the skin; no punctum | Leave it, or excision |
| Boil or abscess | Hot, very tender, swelling over days | Pus, spreading redness, sometimes fever | Prompt medical treatment, sometimes drainage |
| Acne cyst or nodule | Deep, painful lump on the face, chest or back | Other acne nearby; settles over weeks | Acne treatment; see blind pimple |
| Other growths | Hard, fixed, irregular or fast-growing | Unlike a typical cyst | Examined first; imaging or biopsy where needed |
Squeezing empties the cavity and leaves the lining intact, so it refills. Incision and drainage relieves pressure but does not resolve the cyst. Only removal of the wall does.
Size, site, whether it is currently inflamed or infected, previous rupture, and scarring from earlier attempts.
Excision of the intact sac. An acutely inflamed cyst is usually settled first, because operating through inflamed tissue increases the chance of incomplete removal and a worse scar.
There are several ways a cyst can be “treated”, and they do very different things. The key difference is whether the wall of the sac is removed.
| Approach | What it does | Does the cyst come back? | When it is used |
|---|---|---|---|
| Squeezing at home | Pushes some contents out; often ruptures the wall | Yes, usually | Not advised |
| Incision and drainage | A small cut lets pus or contents out and relieves pressure | Often, because the wall stays behind | A painful, swollen, infected cyst, as a first step |
| Small-incision (punch) removal | Contents are emptied and the sac is teased out through a small opening | Uncommon if the whole sac comes out | Smaller cysts that have not been inflamed |
| Elliptical excision | The cyst is cut out whole with a small ellipse of skin and the wound is stitched | Uncommon when the wall is removed intact | Larger cysts, or those scarred by previous inflammation |
Removal is done under local anaesthetic; the injection stings briefly, then you feel pressure rather than pain. The technique depends on size, site and whether the cyst has been inflamed before, because inflammation scars the wall to the surrounding tissue. What matters most for recurrence is that the wall comes out intact.
At IN Eternity Clinic, the approach depends on the cyst itself. A quiet cyst of suitable size and site can be removed in this way under local anaesthetic, once it has been confirmed as a cyst. Very large or deep cysts, cysts in difficult sites, and lumps that do not look typical are referred for surgical or specialist care.
A cyst that suddenly becomes red, swollen, hot and painful has usually leaked keratin into the surrounding skin. Bacteria are sometimes involved, but not always, so antibiotics are not automatically needed. What helps:
A doctor may drain a tense, painful cyst or treat infection where needed. Removal of the sac is planned several weeks later, once the area has settled, when the wall is most likely to come out in one piece.
A cyst that is red, hot, painful or discharging is treated as inflammation first. Cosmetic considerations wait.
General clinical observations used at consultation; they describe what is checked, not any individual result.
At IN Eternity Clinic the first step is to confirm that the lump is a cyst. Lipomas, swollen lymph nodes and, rarely, other growths can feel similar, so size, depth, mobility and the presence of a punctum are checked by hand before anything is planned.
If the cyst is quiet, removal of the whole sac is discussed: where the incision would sit, how it is closed, and how long a scar to expect. If it is inflamed, the plan is to let it settle first, because cutting through inflamed tissue makes it harder to remove the wall completely.
Expect a small stitched wound, a dressing for a few days, and a follow-up to check healing. Stitches on the face are usually removed sooner than on the back or chest. A scar is part of any excision; its length depends on the size of the cyst and where it is.
Recurrence is uncommon when the full wall is removed, but it can happen, particularly after a cyst has ruptured or been drained several times before.
Most cysts are harmless and can be left alone. See a doctor promptly if:
Where any of these apply, the lump is examined first, with imaging, testing or referral where needed.
Cost depends on the size and number of cysts, where they are, whether the cyst needs to settle first, the technique used and whether the tissue is sent to the laboratory. Because these vary, the plan and its cost are set out after the lump has been examined. At IN Eternity Clinic the consultation fee is S$120, waived with any medical treatment.
To have a lump checked, book an assessment with Dr Sin Yong. Other lumps are covered on skin growths, lumps and bumps.
“A cyst that keeps coming back has usually been emptied, not removed. The wall is the part that matters.”
An epidermoid cyst is a sac lined with epidermis, filled with keratin. The contents are not the problem — the wall is.
Squeezing empties the cavity and leaves the lining intact, so it refills. Incision and drainage relieves pressure but does not resolve the cyst. Only removal of the wall does.
Size, site, whether it is currently inflamed or infected, previous rupture, and scarring from earlier attempts.
A cyst that is red, hot, painful or discharging is treated as inflammation first. Cosmetic considerations wait.
It is not advised. Squeezing can rupture the wall into the surrounding skin, which causes inflammation and makes later removal harder. It also leaves the lining in place, so the cyst refills.
Most are benign. A lump that is hard, fixed, growing quickly or different from a typical cyst is examined before treatment, and sent for testing if there is any doubt.
Small cysts sometimes shrink, and some stay the same size for years, but the sac usually remains and can refill or become inflamed. A cyst that does not bother you can be left alone; removal of the whole sac is the only way to resolve it.
The contents leak into the surrounding skin, which often causes painful redness and swelling. Keep it clean, apply warm compresses and do not squeeze. See a doctor if it is very painful, spreading or you feel unwell. Removal is planned once it has settled.
Local anaesthetic is injected first. It stings for a few seconds; after that you should feel pressure and movement but not pain. The area may ache for a day or two afterwards.
Cost depends on the size, number and site of the cysts, whether inflammation must settle first, the technique and laboratory testing. It is set out after examination. At IN Eternity Clinic the consultation fee is S$120, waived with any medical treatment.
These sources describe mechanisms and general evidence. They are not a promise of any individual result; suitability is decided at an in-person assessment.
Every assessment at IN Eternity Clinic is carried out personally by Medical Director Dr Sin Yong at 9 Scotts Road, #12-01 Pacific Plaza. If the honest answer is that treatment should wait, you will be told that.
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