Back Mass or Lump

What causes a lump on the back

The back has a large area of skin and fat, so most back lumps start in those layers. Where on the back the lump sits gives useful clues.

Lipoma

A lipoma is a slow-growing lump of fat cells under the skin. It is the commonest lump on the upper back and shoulders. It feels soft and rubbery, moves slightly when pushed and is usually painless. Some people have several. Lipomas are benign and do not turn cancerous.

Skin cysts

Epidermoid cysts, often called sebaceous cysts, are round, firm lumps attached to the skin, frequently with a small dark pore on top. They are common on the upper back, where the skin is thick. They can become inflamed: red, swollen, painful and leaking a cheesy, smelly material.

Boils and abscesses

A boil is an infected hair follicle that forms a tender, red lump with a yellow head over a few days. An abscess is a larger collection of pus. Recurrent boils on the back can be linked to Staphylococcus aureus carriage, including MRSA, or to diabetes.

Pilonidal cyst

A pilonidal cyst forms at the top of the buttock crease, over the tailbone. Ingrown hairs create a small pit that can become infected, causing a painful swelling and discharge. It is most common in young men and people who sit for long periods.

Lower-back fatty nodules ("back mice")

Small, firm, rubbery nodules over the pelvic bones on either side of the lower spine are called episacral lipomas. They may be tender and are sometimes blamed for low back pain. They are benign.

Muscle knots and spasm

A tight band or knot in the muscles beside the spine (trigger point) can feel like a firm lump. It is tender, may spread pain when pressed, and softens with heat, massage and stretching.

Bony lumps along the spine

The bony points of the spine (spinous processes) are easy to feel, especially at the base of the neck, where the C7 vertebra sticks out. A rounded hump high on the back can be kyphosis or a fatty pad at the base of the neck. A rib or shoulder blade that sticks out on one side can be a sign of scoliosis.

Rare causes

• Soft tissue sarcoma: a painless, growing, firm mass, often deep to the muscle and larger than 5 cm.
• Dermatofibrosarcoma protuberans: a slow-growing, firm, purplish or skin-colored plaque on the trunk.
• Skin cancers, including melanoma, which is common on the back because it is hard to see.
• Spinal tumors and cancer spread to the spine: these cause night pain and nerve symptoms more often than a visible lump.
• A lump at the base of the spine in a baby may be a sign of a hidden spinal cord problem (such as spinal dysraphism) and should be checked.

Comparing common back lumps

When to worry about a lump on your back

Get a lump checked if it:

• is larger than 5 cm (about the size of a golf ball)
• is getting bigger
• feels hard and fixed, or sits deep under the muscle
• comes back after removal
• comes with unexplained weight loss, fever or night sweats
• comes with back pain that is worse at night or at rest

Ask someone to look at your back skin regularly, or use a mirror, because moles there are easy to miss.

How a back lump is diagnosed

A doctor examines the lump's size, texture, depth and mobility, the skin over it, and nearby lymph nodes. If the spine might be involved, they check leg strength, sensation and reflexes.

• Ultrasound is the usual first test. It distinguishes fat, fluid and solid tissue.
• MRI is used for deep or large lumps, lumps near the spine, and before surgery for a possible sarcoma.
• X-ray or CT if a bone problem is suspected.
• Biopsy confirms the diagnosis when a lump looks unusual. For a possible sarcoma, this is done at a specialist center.

Treatment

• Lipomas and small cysts: no treatment unless they bother you. They can be removed under local anesthetic in a short outpatient procedure.
• Inflamed or infected cysts and abscesses: warm compresses for mild inflammation. Larger abscesses need incision and drainage, and antibiotics if there is spreading redness.
• Pilonidal cyst: drainage for an abscess, then surgery or other procedures to remove the tract if it keeps recurring. Hair removal in the area helps prevent return.
• Muscle knots: heat, massage, stretching and posture changes.
• Cancers: surgery at a specialist center, often with radiotherapy or other treatment.

Do not squeeze or try to cut open a lump yourself. It can spread infection and makes later removal harder.

Frequently asked questions

What is a soft lump on my back?

A soft, movable, painless lump on the back is most likely a lipoma, a harmless collection of fat cells. It grows slowly over months or years. Have it checked if it is larger than 5 cm, growing, hard or painful.

Is a lump on the spine serious?

Most lumps over the spine are skin cysts, lipomas or the normal bony points of the vertebrae. A lump with back pain at night, weight loss, or leg numbness or weakness needs prompt assessment and usually an MRI. Loss of bladder or bowel control is an emergency.

What causes a hard lump on the lower back?

Firm lumps on the lower back are often epidermoid cysts, episacral lipomas over the pelvic bones, or muscle knots. A painful swelling at the top of the buttock crease is usually a pilonidal cyst. A hard, fixed or growing lump should be checked with an ultrasound.

Can a back lump be cancer?

It can, but this is uncommon. Warning signs are a lump that grows, is larger than 5 cm, feels hard and fixed or sits under the muscle, or comes back after removal. Changing moles on the back can be melanoma and should be checked promptly.