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Sebaceous Cyst: The Common Lump Under the Skin

  • Prof. Dr. Zahid Mahmood
  • August 3, 2026

Sebaceous Cyst: The Common Lump Under the Skin

By Prof. Dr. Zahid Mahmood — General, Laparoscopic & Laser Surgeon, Lahore

A sebaceous cyst is probably the single most common lump I’m asked to remove in my clinic. Patients usually notice a smooth, slow-growing swelling under the skin — on the scalp, face, neck, back, or occasionally the scrotum — and want to know whether it’s dangerous, why it keeps coming back after they’ve tried to squeeze it, and what the actual treatment involves. The good news is that this is one of the most straightforward, low-risk conditions in general surgery to treat properly — but “properly” is the key word, and a poorly done removal is exactly why so many patients end up with the same lump reappearing months or years later.

What a “sebaceous cyst” actually is

I want to start with an honest clarification, because the everyday name for this condition is technically a bit misleading. What most people call a “sebaceous cyst” is not actually derived from a blocked sebaceous (oil) gland at all — it’s properly called an epidermal cyst. It forms from skin cells lining the upper part of a hair follicle, or occasionally from skin cells that become trapped beneath the surface after a minor injury. These cells continue to behave exactly as normal skin cells do, quietly producing keratin — the same tough protein that makes up the outer layer of your skin and your nails — but with nowhere to shed it. Over time, this keratin builds up inside a sac under the skin, forming a slow-growing, round, firm-but-mobile lump. The name “sebaceous cyst” has simply stuck in everyday language, even though the sebaceous glands themselves are rarely the actual source.

A very similar but distinct type of cyst, called a trichilemmal or pilar cyst, arises specifically from the outer sheath of a hair follicle rather than the surface skin layer. These are especially common on the scalp — around 9 in 10 occur there — and unlike the more general epidermal cyst, they are frequently multiple, with several appearing at once or over time in the same person. In everyday practice, distinguishing precisely between an epidermal cyst and a pilar cyst rarely changes what I do — both are managed the same way — and the distinction is usually only confirmed afterward, when the removed tissue is examined under the microscope.

Who tends to get them, and why

Sebaceous cysts can develop in anyone, but they’re seen more often in adults than children, and more often in men than women. Areas of skin that have previously been through some form of trauma, or that are particularly prone to acne and blocked follicles, seem more likely to develop them, since both a healed injury and a chronically blocked follicle can trap a small nest of skin cells beneath the surface. Some people are simply more prone to forming these cysts than others for reasons that aren’t fully understood, and having had one in the past doesn’t prevent a completely new one from forming elsewhere later — this is a different situation from a single cyst recurring in the exact same spot, which, as explained below, usually points to incomplete removal rather than a new cyst forming independently.

How to recognise one

A typical sebaceous (epidermal) cyst is a smooth, round, slow-growing lump that sits just under the skin and moves slightly when pushed, though it is tethered to the skin itself rather than floating freely in the deeper tissue the way a lipoma does. A very characteristic and useful clue is a tiny, often dark central pore visible on the overlying skin, called a punctum — this is the residual opening of the original hair follicle from which the cyst arose, and its presence is one of the most reliable ways to tell a sebaceous cyst apart from other lumps on clinical examination alone. These cysts can occur almost anywhere on the body that has hair-bearing skin, though the scalp, face, neck, back, and scrotum are by far the most common locations.

Left alone, an uninflamed cyst is usually entirely painless and causes no problems beyond its appearance — some patients live with small ones for years without any trouble at all. The difficulty arises when the cyst becomes inflamed or infected, which happens fairly often over time. At that point, it becomes red, tender, warm, and can swell rapidly and quite dramatically, sometimes discharging a thick, foul-smelling, cheese-like material — this is the accumulated keratin, not pus in the traditional sense, though a true secondary bacterial infection with genuine pus can also develop on top of it.

“Is this a sebaceous cyst or a lipoma?”

This is one of the most common questions I’m asked, since both present as a slow-growing, painless lump under the skin, and patients understandably can’t always tell the two apart themselves. A lipoma is a benign lump of fatty tissue that develops in the deeper layer under the skin rather than within the skin itself. On examination, the two usually feel quite different: a sebaceous cyst is tethered to the overlying skin, often has that tell-tale central punctum, and feels firmer; a lipoma tends to sit more freely in the deeper tissue, has a softer, doughy feel, moves more easily under the fingers, and has no visible punctum on the skin above it. The distinction matters for planning treatment, since the surgical approach to removing each is slightly different, but in practice a careful clinical examination is usually enough to tell them apart before ever picking up a scalpel.

Why squeezing it yourself is a bad idea

I understand the temptation — a lump that looks like it has a visible pore is naturally tempting to squeeze, especially when it’s inflamed and uncomfortable. But doing this rarely empties the cyst properly, since the sac wall producing the keratin remains behind regardless of how much material is squeezed out through the small punctum. What squeezing often does achieve is introducing bacteria into an already irritated area, converting a simple inflamed cyst into a genuinely infected one, sometimes with a proper abscess requiring drainage. If a cyst is bothering you, the better path is to have it assessed properly rather than attempting to manage it at home.

Why it keeps coming back after some treatments

This is one of the most important things to understand about sebaceous cysts: the swelling you can feel is not the whole problem — it’s the visible sign of a thin sac (the cyst wall) lying beneath the skin, and that wall is what continuously produces the keratin filling the cyst. If any part of that wall is left behind during removal, the cells lining it carry on doing exactly what they were doing before, and the cyst — or something very like it — reliably grows back in the same spot, sometimes after a gap of months or years that can fool a patient into thinking it’s been successfully cured. Complete removal of the entire cyst wall, not just draining or scooping out its contents, is what determines whether a cyst is truly gone for good.

Treatment: timing matters as much as technique

How I approach treatment depends heavily on whether the cyst is calm or acutely inflamed at the time I see it.

For a calm, uninflamed cyst, straightforward surgical excision is the right approach, and it can usually be done there and then. Under local anaesthetic, an incision is made over the cyst, and the entire sac — including its wall and the punctum on the overlying skin — is carefully separated from the surrounding tissue and removed intact wherever possible. Because the whole point is to take the sac out complete and unruptured, this is generally easier and gives a cleaner result when the cyst is dealt with in this quiet, non-inflamed state, with a small, neat scar and a low chance of recurrence.

For an acutely inflamed or infected cyst, jumping straight to a full excision is usually the wrong move — trying to dissect out an intact cyst wall through swollen, friable, infected tissue is difficult, more likely to leave fragments of the wall behind, and more likely to result in a messier wound and scar. The better approach in this situation is to first drain the cyst, relieving the pressure and clearing out the built-up keratin and any pus, and let the inflammation settle over the following weeks with simple wound care and antibiotics if there’s a genuine bacterial infection. Once the area has calmed down and the tissue has returned to something closer to normal, a planned, complete excision of the (by then empty) cyst wall can be performed properly — this two-stage approach, treat the acute flare-up first and remove the underlying sac later, gives far better long-term results than attempting a difficult, one-step removal in the middle of active inflammation.

What the procedure itself involves

Removal of an uncomplicated sebaceous cyst is a minor procedure, almost always done under local anaesthetic as a day case. A small incision is made, often deliberately designed to include and remove the punctum itself, since leaving even that small residual opening behind can occasionally be enough for the cyst to reform. The sac is then carefully dissected free from the surrounding tissue — ideally without rupturing it, since an intact removal is both tidier and gives the most reassurance that nothing has been left behind — and the small wound is closed with a few sutures. The whole procedure typically takes well under an hour, and patients go home the same day with simple aftercare instructions.

A note on cysts on the face

Facial sebaceous cysts deserve a special mention, since patients are understandably more concerned about scarring in a visible area than they might be for the same lump on the back or scalp. The good news is that planned, unhurried removal of a calm facial cyst generally gives an excellent cosmetic result — a small, carefully placed incision along the natural lines of the skin heals into a fine, barely noticeable line over time in the great majority of patients. This is precisely why I’m keen to treat facial cysts electively, while they’re calm, rather than have them progress to an inflamed, swollen state that then needs urgent drainage — an emergency drainage procedure on an acutely inflamed facial cyst is far more likely to leave a visibly worse scar than a calm, planned excision would have.

What happens to the tissue afterward

Once removed, I routinely send the excised cyst for pathological examination. This isn’t because these cysts are commonly dangerous — the overwhelming majority are entirely benign, and genuine malignant change within a long-standing sebaceous cyst is very rare — but it’s good, careful practice to confirm exactly what the tissue is, particularly for a lump that has been present for a long time, has grown quickly, or looks in any way atypical on examination. This is a routine precaution rather than a cause for alarm.

A less common pattern worth knowing about

Occasionally, a patient presents with numerous sebaceous or epidermal cysts appearing over the trunk and limbs over a period of years, sometimes alongside other benign fatty lumps (lipomas). In a small number of these patients, this pattern can be one feature of a rare inherited condition affecting the bowel, and it is worth mentioning to your doctor if multiple cysts of this kind run in your family, or if you have a personal or family history of colon polyps or bowel cancer at a young age — this context can occasionally prompt a wider conversation about screening, even though the great majority of people with several sebaceous cysts have no such underlying condition at all.

What to expect during recovery

Recovery from a straightforward cyst excision is quick and uneventful for most patients. Mild discomfort at the site for a few days is normal, usually well controlled with simple painkillers, and the small wound is typically kept clean and covered with a simple dressing until the stitches are either removed or dissolve, generally within about five to seven days on the face, and somewhat longer — around ten to fourteen days — on the scalp, back, or scrotum, where the skin is under a bit more tension and takes slightly longer to hold securely on its own. Scalp and back wounds in particular should be kept clean and dry initially, and I advise avoiding vigorous rubbing, tight headwear, or heavy lifting immediately around the wound until it has properly settled. If the area becomes increasingly red, painful, or starts discharging again after the wound has initially settled, that’s worth a follow-up review rather than assuming it will resolve on its own.

Warning signs worth getting checked

  • A slow-growing, smooth lump under the skin, especially one with a visible central pore
  • A lump that suddenly becomes red, tender, warm, or rapidly larger
  • Discharge of thick, foul-smelling material from a lump
  • A cyst that keeps recurring in the same spot after previous treatment
  • A lump that is hard, fixed to deeper tissue, rapidly growing, or otherwise doesn’t fit the typical picture described above
  • Multiple such cysts appearing over the years, particularly alongside a family history of bowel problems

What you should do

If you’ve noticed a lump that sounds like this, there’s no need to live with the uncertainty, and there’s no need to attempt to squeeze or drain it yourself. A calm, uninflamed cyst can usually be assessed and, if appropriate, removed completely and cleanly in a single straightforward visit. An inflamed or already-discharging cyst still deserves proper attention, even though the definitive removal may need to wait a few weeks until the inflammation has settled — either way, getting it looked at early, rather than repeatedly self-treating a recurring lump, is what gives the best chance of a lasting result with minimal scarring.

To book a consultation with Prof. Dr. Zahid Mahmood, call 0300 413 0159 or visit professorzahid.com.

This article is for general awareness and does not replace a personal medical consultation.

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