Lipoma or Cyst? How to Tell the Difference
Lipomas and epidermoid cysts are the two lumps most often confused with each other. They feel different, sit at different depths, and are treated differently.
Two lumps account for the overwhelming majority of soft tissue bumps people find on themselves: lipomas and epidermoid cysts. They are both benign and both common, and they are regularly mistaken for one another.
How they differ
What they are made of
A lipoma is a growth of fat cells inside a thin capsule. A cyst is a sac lined with skin cells that fills with keratin, the same protein your skin and nails are made of. Different tissue, different behaviour.
How they feel
A lipoma is soft, doughy and slides freely under your fingertip. A cyst tends to feel firmer and rounder, and sits more superficially, closer to the surface of the skin.
Whether there is a visible pore
This is the most useful single clue. Epidermoid cysts often have a tiny central opening, called a punctum, visible on the skin over them. Lipomas never do, because they sit deeper and have no connection to the surface.
Whether they get inflamed
Cysts commonly become red, tender and swollen, and can discharge a thick, foul-smelling material. Lipomas essentially never do this. A lump that has flared up repeatedly is far more likely to be a cyst.
Depth
Lipomas sit in the subcutaneous fat, so the skin moves independently over them. Cysts are attached to the skin, so moving the skin moves the lump.
Why the distinction matters for treatment
Both are removed by excising the whole thing, including its wall or capsule. The difference is in the details.
An inflamed cyst usually needs the inflammation settled before removal, because operating through actively infected tissue leads to a worse scar and a higher chance of recurrence. A lipoma can be removed whenever it suits you.
In both cases, incomplete removal is what causes recurrence. A drained cyst whose wall is left behind will refill. A lipoma whose capsule is left behind can regrow.
When to get it looked at properly
Self-diagnosis is fine for reassurance and not enough for decisions. Get any lump assessed if it is growing quickly, has become firm or fixed, is painful without explanation, is larger than about 5 cm, or you simply do not know what it is.
Examination is usually enough. Ultrasound settles most of the remaining cases quickly, and pathology after removal gives the definitive answer.
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