A lump beneath the skin is common and is often benign, but it should be assessed if it is new, increasing in size, painful, firm or otherwise changing. Lipomas and skin cysts are frequent causes, although swollen lymph nodes, inflammation and other soft-tissue growths can look similar. A clinical examination helps establish whether reassurance, imaging, monitoring or removal is appropriate.

What might be causing the lump?

A lipoma is a soft, fatty lump that usually moves slightly beneath the skin. An epidermoid or pilar cyst is a sac within the skin that may feel firm and sometimes has a visible central opening. Other possibilities include a benign soft-tissue tumour, enlarged lymph node, scar tissue, inflamed tissue or, less commonly, a malignant mass. It is not possible to confirm the diagnosis from appearance alone.

Features that should be assessed

Arrange an appointment if the lump is growing, painful, hard, fixed, deep, irregular or larger than approximately 5 cm. Changes to the overlying skin, unexplained weight loss or a lump that returns after previous removal also need review. Most lumps are not cancer, but early assessment of concerning features supports the correct referral and investigation.

How is a lump investigated?

Your surgeon will ask when you first noticed it, whether it has changed and if it causes discomfort. Examination considers size, depth, mobility, skin changes and its relationship to nearby structures. Ultrasound is often useful for a superficial lump. MRI or another investigation may be recommended for deeper, larger or uncertain masses. Sometimes a biopsy or complete excision is needed for diagnosis.

What treatment may be offered?

A small lump with reassuring features may be monitored. Removal may be considered if it is painful, enlarging, repeatedly inflamed, affecting movement or causing concern. The tissue is commonly sent to a laboratory for histology after excision. The approach and scar depend on the size, depth and location of the lump.

When is urgent help needed?

Seek prompt medical advice for a rapidly enlarging mass, severe pain, spreading redness, fever or signs of infection. A suspected soft-tissue sarcoma requires urgent specialist referral rather than routine office removal.

Frequently asked questions

Are most lumps under the skin harmless? Yes, many are lipomas or cysts, but a new or changing lump should still be assessed.

Can ultrasound tell whether it is a lipoma? Ultrasound can often clarify a superficial lump, but additional imaging or histology may sometimes be required.

Should every lump be removed? No. Removal depends on diagnosis, symptoms, growth and patient preference.