Lump or Mass: Common Causes and When to Worry

How to describe your lump

Doctors learn a lot from a few features. Note these before your appointment:

Common causes of a lump under the skin

Lipoma

A lipoma is a slow-growing lump of fat cells. It feels soft and doughy, moves when pushed, and is usually painless. Lipomas are most common on the shoulders, back, upper arms, thighs and neck, and many people have more than one. They are harmless and only need removal if they are large, uncomfortable or growing quickly. A lipoma on a partner's leg or hip has no effect on fertility.

Skin cysts

An epidermoid cyst (often called a sebaceous cyst) is a round lump in the skin, often with a small dark central pore. It can be squeezed or burst and release cheesy, smelly material. Cysts can become red and painful when inflamed or infected. Pilar cysts are similar but form on the scalp.

Swollen lymph nodes

Lymph nodes in the neck, armpits and groin swell when fighting infection, for example after a sore throat or a cut on the leg. They feel like soft, tender beans and settle within 2 to 3 weeks. Nodes that are hard, rubbery, painless, growing, or larger than about 2 cm (0.8 in) need checking for lymphoma or spread of cancer. See swollen lymph nodes.

Ganglion cyst

A ganglion cyst is a jelly-filled sac attached to a joint or tendon, usually on the back of the wrist, the palm side of the wrist, a finger or the top of the foot. It can come and go, and may get bigger with activity.

Abscess

An abscess is a pocket of pus. It is red, hot, swollen and painful, and often grows over a few days. It may come to a head. Most need to be drained by a clinician.

Hernias

A hernia is tissue pushing through a weak spot in the belly wall. An inguinal hernia appears in the groin, gets bigger when you stand, cough or strain, and usually shrinks or disappears when you lie down. A groin lump that does this is very likely a hernia. A swollen lymph node does not change with coughing.

Injury-related lumps

A knock can leave a hematoma (collection of blood) that feels firm and tender and slowly shrinks over weeks. Sometimes the area hardens with calcium (myositis ossificans), especially in the thigh after a deep bruise.

Muscle bulge

A bump on the forearm or upper arm that appears only when you tense the muscle is usually a muscle hernia: muscle pushing through a small gap in its covering (fascia). It is harmless unless painful.

Less common but important causes

• Soft tissue sarcoma: a rare cancer of fat, muscle or connective tissue. It is usually a painless, growing lump deep in the thigh, buttock, arm or trunk. Any deep lump larger than 5 cm (2 in), or any growing lump, should have an ultrasound. See soft tissue sarcoma.
• Lymphoma: painless, rubbery lymph nodes, often with night sweats, fever or weight loss.
• Skin cancers: a lump in the skin that bleeds, crusts, changes color or does not heal.
• Spread of cancer to lymph nodes or skin from another organ.
• Bone tumors: a hard swelling over a bone with deep, night-time bone pain.

Lumps by location

Lump on the shoulder

A small, hard lump on the shoulder is often an epidermoid cyst in the skin. A soft, larger lump is often a lipoma. A bump at the top of the shoulder after a fall may be a separated AC joint. A lump above the collarbone (supraclavicular) should always be checked, because lymph nodes there can signal problems in the chest or abdomen. See shoulder lump.

Lump on the arm under the skin

Lipomas, cysts and muscle hernias are the most common. Swollen lymph nodes occur near the elbow (epitrochlear) and in the armpit. A ganglion forms at the wrist.

Lump on the leg or lower leg

A painless lump on the lower leg is often a lipoma, cyst, or a lump left after an old bruise. A Baker's cyst causes swelling behind the knee. Varicose veins form soft, bluish bulges that empty when you lift the leg. Red, tender lumps on the shins can be erythema nodosum, a reaction to infection, medicines or inflammatory bowel disease. A deep, firm, growing lump in the thigh needs imaging to rule out sarcoma.

Lump on the toe or next to the big toe

A bony bump at the base of the big toe is usually a bunion. Other causes include gout (a red, hot, very painful swelling, often overnight), a ganglion or mucous cyst, a corn or callus, and bone spurs from arthritis. A dark or bleeding growth under or near a toenail needs checking for melanoma.

Lump in the groin

Most groin lumps are hernias or lymph nodes. Hernias bulge with coughing and can often be pushed back. Lymph nodes do not, and are often tender with an infection of the leg, foot or genitals. See groin mass.

Lumps on the tongue

Enlarged taste buds (lie bumps), small cysts and injury from biting are common and settle within 2 weeks. When to worry about tongue lumps: a lump or sore that lasts more than 3 weeks, is hard, bleeds, or is a white or red patch, especially in smokers and drinkers, needs an exam to rule out oral cancer.

How doctors assess a lump

Your doctor will ask how long it has been there, whether it has changed, and about pain, injury, infection and general symptoms. They will feel its size, depth, firmness and mobility, and check nearby lymph nodes.

• Ultrasound is the first test for most lumps. It can show whether it is fat, fluid or solid tissue.
• MRI shows deep lumps and their relation to muscle and bone.
• Biopsy (a needle sample) is done if imaging is unclear or concerning. Suspected sarcomas should be biopsied at a specialist center.
• Blood tests if infection, lymphoma or gout is suspected.

Treatment

Treatment depends on the cause. Lipomas and cysts can be left alone or removed under local anesthesia. Abscesses are drained. Hernias are repaired surgically. Ganglions may be watched, drained or removed. Infections are treated with antibiotics when needed. Cancers are treated by specialist teams.

Do not squeeze or try to cut out a lump yourself. It can cause infection and scarring and may delay diagnosis.

Frequently asked questions

When should I worry about a lump under my skin?

See a doctor if a lump is larger than 5 cm (2 inches), is hard and fixed, has grown over weeks, is deep within muscle, keeps coming back, or comes with weight loss, fever or night sweats. Also get any lump checked that has been present for more than 2 to 3 weeks without explanation.

Are painless lumps more dangerous than painful ones?

Not necessarily. Painful lumps are often from infection or injury, which is reassuring. Many cancers are painless, but so are most lipomas and cysts. Size, growth, depth and hardness tell doctors more than pain does.

How can I tell if a groin lump is a hernia or a lymph node?

A hernia usually gets bigger when you stand, cough or strain, and shrinks or disappears when you lie down. A lymph node stays the same, feels like a bean, and is often tender when there is an infection nearby. An ultrasound confirms which it is.

What is a lump that appears only when I flex my arm muscle?

This is usually a muscle hernia, where a small part of the muscle bulges through a gap in its outer covering when it contracts. It is harmless and needs treatment only if it causes pain. An ultrasound can confirm it.

What should I do about a lump in my leg?

Note its size, feel and whether it is changing. Soft, movable, stable lumps are usually lipomas or cysts. See a doctor for an ultrasound if it is deep, firm, larger than 5 cm (2 in), growing, or painful without an injury. Get urgent care if your calf is swollen, hot and painful, which may be a blood clot.

Can a lump go away on its own?

Yes. Swollen lymph nodes from infection, bruises and some cysts shrink over days to weeks. Lipomas and most cysts stay or grow slowly. Any lump that persists beyond 2 to 3 weeks without a clear cause should be checked.