Symptoms · Skin
A soft lump under the skin
The short answer
A soft, slow-growing, painless lump under the skin is most often a lipoma (a fatty lump) or a sebaceous cyst (a blocked oil gland). Both are harmless and can be left alone. They can be removed under local anaesthesia if they grow, hurt, get infected, or bother you. See a doctor for any lump that is hard, fixed, growing fast or painful, or larger than about 5 cm.
How patients describe it
- A soft ball under my skin
- A lump on my back, neck or arm
- A bump with a small dark dot
- A lump that slowly gets bigger
- A boil that keeps coming back
See a doctor soon if you have
- A lump that is hard, fixed, or growing fast
- A lump larger than about 5 cm, or deep under the muscle
- Pain, redness, heat or pus over the lump
- Fever with a red, painful lump (go to the emergency room)
- A lump that bleeds, or skin over it that breaks down
What can cause it
Lipoma
A soft, rubbery, painless lump that moves under the skin and grows slowly.
Next step: Examination; removal only if it bothers you.
Sebaceous cyst
A round lump with a tiny dark dot in the middle. It can leak cheesy material or become infected.
Next step: Examination; removal when it is large, recurrent or infected.
Boil or abscess
A hot, red, painful lump that may come to a head.
Next step: See a doctor; it may need to be drained.
Swollen lymph node
A tender lump in the neck, armpit or groin, often with an infection nearby.
Next step: Examination; it usually settles when the infection clears.
What you can do now
- Do not squeeze or cut a cyst yourself, because this can cause infection
- Use a warm compress on a red, tender cyst
- Note when you first saw the lump, and take a photo next to a coin to show its size
- See a surgeon if it grows, hurts, gets infected, or bothers you
Tests your doctor may order
- Examination of the lump
- Ultrasound if the diagnosis is unclear
- Laboratory examination of the lump after it is removed
When is surgery needed?
- Removal is a short operation under local anaesthesia, usually 20–30 minutes, and fasting is not required.
- The whole sac is removed to lower the chance of it coming back. It comes back in about 1–5 in 100 people.
Related operation guides
Questions people ask
Will it go away by itself?
Lipomas and cysts usually do not disappear. They are harmless and can be left alone unless they bother you.
Does removal leave a scar?
Yes, a small scar. Your surgeon will plan the cut to keep it as small and as hidden as possible.
Can a cyst get infected?
Yes. A red, hot, painful cyst or one with pus needs to be seen by a doctor, because it may need to be drained.
This page gives general information and does not replace the advice of your treating team. In an emergency, go to the nearest emergency room.