Finding a new lump under the skin is one of the most common reasons people seek a surgical opinion — and understandably one of the most anxiety-provoking. The reassuring news is that the overwhelming majority of lumps felt just beneath the skin are entirely benign. Even so, knowing what the common ones are, how they tend to behave, and which features genuinely warrant review helps you tell the difference between something harmless and something worth having checked.
Epidermoid cysts (the "sebaceous cyst")
Often referred to as sebaceous cysts, epidermoid cysts are among the most common lumps of all. They typically feel like a smooth, round, firm lump that moves with the skin, and there is sometimes a small dark dot (a punctum) visible on the surface where the cyst connects to the skin. They form when skin cells and a protein called keratin become trapped beneath the surface, gradually building up into a sac.
Epidermoid cysts are harmless, but they can slowly enlarge over months or years, and they occasionally become inflamed or infected — at which point they may turn red, swollen and tender, and sometimes discharge. An inflamed cyst is best assessed before any planned removal, as surgery is more straightforward once any inflammation has settled.
Lipomas
A lipoma is a soft, fatty lump that sits in the layer of fat just beneath the skin. They are very common and benign. A lipoma typically feels soft, smooth and rubbery, moves easily under the fingers, and is usually painless. They grow slowly and can appear almost anywhere on the body, most often on the trunk, shoulders, neck and limbs. Some people develop several over their lifetime.
Most lipomas need no treatment at all. They can, however, be removed if they are large, growing, sitting in an awkward or visible spot, causing discomfort, or simply bothersome to the person who has one.
Other common lumps
Several other benign lumps are frequently seen in clinic:
- Dermatofibroma: a small, firm nodule, most often on the lower legs, that can feel like a hard little button under the skin. Pinching the skin around it often produces a characteristic central dimple. They are harmless and usually need no treatment.
- Ganglion: a fluid-filled swelling that arises near a joint or tendon, most commonly around the wrist or back of the hand. They are benign and may fluctuate in size.
- Enlarged lymph nodes: small glands that can swell in response to a nearby infection, such as a sore throat or a skin infection. Most settle on their own once the cause resolves, but a node that remains enlarged for more than a few weeks should be assessed.
- Abscess: a tender, hot, red and often rapidly developing collection of infection that usually needs prompt treatment rather than routine assessment.
Reassurance: most lumps are harmless
The features that make a lump very likely to be benign are common and reassuring: it has been present for a long time without changing, it feels soft or rubbery, it moves freely under the skin, it is not painful, and the skin over it looks completely normal. A lump that ticks these boxes is rarely anything to worry about, although it can still be removed if it is a nuisance.
Red flags: when to seek review
A small number of features make a lump worth having reviewed without delay. None of these means a lump is cancerous — most still turn out to be benign — but they are the features that warrant a proper assessment and sometimes a scan:
- Rapid growth over a matter of weeks
- A lump larger than around five centimetres (roughly the size of a golf ball)
- A hard lump, or one that feels fixed and does not move
- A lump that sits deep and feels attached to the underlying muscle or tissue
- Persistent or increasing pain
- Changes in the overlying skin, such as colour change, dimpling or ulceration
- A long-standing lump that suddenly starts to change
As a simple rule of thumb, any lump that is larger than a golf ball, deep, hard or growing deserves a specialist assessment. Most are still benign, but these are precisely the features that, very occasionally, point to a soft-tissue tumour that needs imaging before anything else is done.
"Most lumps under the skin are harmless and have been there far longer than people realise. The ones worth checking are those that grow, harden or change — when in doubt, it is always reasonable to have a lump examined."
How lumps are assessed
Most lumps can be diagnosed confidently by examination alone, taking into account how long they have been present, how they feel and how they behave. Where there is any uncertainty — particularly for lumps that are deeper, larger or growing — an ultrasound scan is a simple, painless first investigation, and occasionally a magnetic resonance imaging (MRI) scan is arranged to look at a lump in more detail. If a tissue diagnosis is needed, a biopsy can be taken. This careful, stepwise approach means that the rare lump that needs more attention is identified early, while the many that do not can be managed simply.
Treatment and removal
Many benign lumps need no treatment beyond reassurance. When removal is appropriate — for diagnosis, for symptoms, or for cosmetic reasons — it is usually a straightforward procedure carried out under local anaesthetic as a day case. A cyst is removed together with its full wall to reduce the chance of it returning, and a lipoma is removed through a small incision over the lump. Mr Singh will discuss the likely scar, the recovery and the expected outcome before any procedure, so you can make an informed choice.
Conclusion
A new lump is rarely a sign of anything serious, but it is always reasonable to have one examined — both for peace of mind and to identify the small number that benefit from closer attention. If you have a lump you would like assessed, or one that has changed, you can arrange a consultation to have it examined and, where appropriate, removed. You can read more about the procedures involved on our pages covering cyst removal, lipoma removal and benign skin lesion removal. If your concern is a mole or pigmented spot rather than a lump, our guide on when to worry about a mole is a useful companion.
