Skin lumps and cysts

Also called Lipoma, Sebaceous cyst, Epidermoid cyst, Skin tags

Most lumps under the skin are harmless. The features that matter are size, depth, growth and pain, and they are worth knowing.

What it is

A group of common benign lumps.

**Lipomas** are soft, rubbery, mobile lumps of fat under the skin, usually painless and slow-growing. They are extremely common and harmless.

**Epidermoid and pilar cysts**, often loosely called sebaceous cysts, are firm lumps containing keratin, often with a small central punctum. They can become inflamed and infected, and an infected cyst is red, hot, painful and often discharges foul material.

**Skin tags** are small soft outgrowths in skin folds, entirely harmless, more common with age, obesity and diabetes.

The reason they are grouped here is the discrimination that matters. **A lump that is over about 5 centimetres, deep rather than just under the skin, growing, hard, fixed, or painful needs imaging before anybody removes it**, because that is the pattern of a soft tissue sarcoma. Removing a sarcoma as if it were a lipoma compromises the definitive treatment.

Inflamed cysts should not usually be excised while acutely infected; drainage first, excision later, reduces recurrence and scarring.

Multiple painful lipomas can indicate Dercum's disease or lipoedema, and multiple lumps along nerves can indicate neurofibromatosis.

Signs you might notice

Lipoma: soft, rubbery, mobile, painless, slowly growing, just under the skin.

Epidermoid cyst: firm, round, with a central punctum, sometimes discharging cheesy material with a strong smell.

Infected cyst: red, hot, painful, swollen, sometimes discharging pus, occasionally with fever.

Skin tag: small, soft, on a stalk, in a skin fold.

**Needing urgent imaging and referral: a lump over 5 centimetres; a lump that feels deep or fixed; one that is growing; one that is hard; one that is painful; or one that has recurred after removal.**

Also assess: a lump with overlying skin changes, ulceration or bleeding; rapid growth; or a lump in a child.

Urgent: an infected cyst with spreading redness and fever.

How it can affect day-to-day life

Most lumps need nothing but an explanation, and knowing which features would matter converts ongoing anxiety into a simple rule to watch for.

NHS removal of asymptomatic benign lumps is usually not funded, which frustrates people. Removal is offered where a lump is painful, recurrently infected, interfering with function, or diagnostically uncertain.

Cysts that have been infected once tend to recur, and the definitive treatment is excision of the whole cyst wall when it is quiet, not incision when it is inflamed.

Skin tags can be removed simply, and treating them at home with threads or over-the-counter kits risks bleeding and infection, particularly in people with diabetes.

For anybody with a bleeding or ulcerating lump, or a lump that has changed, the question is whether it is a skin cancer rather than a cyst; see non-melanoma skin cancer and melanoma.

The most important practical habit is measuring: writing down the size and date, so growth can be judged rather than guessed.

Supporting someone well

Learn the rule: over 5 centimetres, deep, growing, hard, fixed or painful means imaging first.

Measure a lump and write down the size and date, so change is measurable.

Do not have a suspicious lump removed without an ultrasound or MRI first.

Get an infected cyst drained, and consider excision later when it has settled.

Do not remove skin tags at home, particularly with diabetes.

Get any bleeding, ulcerating or changing lump assessed for skin cancer.

Ask about removal where a lump is painful, recurrently infected or interfering with function.

Get multiple painful lumps, or lumps along nerves, assessed rather than accepted.

Where to get help

A GP practice for assessment; dermatology or surgery for removal.

Urgent referral and imaging for any lump meeting the concerning criteria.

Same-day care for an infected cyst with spreading redness or fever.

British Association of Dermatologists publish patient leaflets on cysts and lipomas.