What should you know about a large lump under the skin?

A lump may be a cyst, a fatty growth, an enlarged structure, a blocked or inflamed follicle, or an infection such as a boil. Some lumps are close to the surface and move slightly under the fingers; others are deeper or attached to nearby tissue. A basal cell carcinoma more often appears as a changing skin growth or sore on sun-exposed skin, but appearance alone cannot diagnose it. The location, duration, firmness, mobility, skin colour, pain, and any drainage help a clinician decide whether examination, imaging, or sampling is needed.

Do not squeeze, pierce, or repeatedly massage the lump. Take a clear photograph and note its size, location, tenderness, and whether the skin is changing. Arrange a medical review for a lump that persists, enlarges, returns, or interferes with movement or clothing. Treatment depends on the cause: an infection may need specific care, while selected inflammatory or scar-related lumps may be considered for an injection into the skin. Avoid using leftover antibiotics or steroid creams without advice.

Seek same-day advice for a hot, red, very painful lump, pus, fever, or redness spreading into nearby skin. Get prompt assessment if it grows quickly, becomes hard or fixed, bleeds, ulcerates, or repeatedly crusts. Emergency care is needed for severe illness, rapidly spreading swelling, or symptoms affecting breathing or swallowing. A painless lump still deserves review when it is new, persistent, or changing.

What features suggest a cyst, boil, scar, or another growth? Does it need imaging or a sample? Should I keep it covered? Which changes would mean I should return sooner?