Quick Summary
- A lipoma is a soft, slow-growing lump made of fat tissue, movable under the skin, and generally painless.
- A cyst (commonly an epidermoid cyst) is a firmer, round lump with a sac beneath the skin, often with a visible central pore, and can become inflamed or infected.
- Lipomas feel soft and doughy; cysts tend to feel firmer and more defined.
- Cysts can sometimes drain a thick, foul-smelling material if squeezed or infected — lipomas do not.
- Both are usually benign, but a lump that's hard, fixed in place, rapidly growing, or painful deserves prompt evaluation.
Finding a new lump under the skin is unsettling no matter what it turns out to be, and lipomas and cysts — the two most common causes — are both usually completely benign. Telling them apart mostly comes down to how they feel.
What a Lipoma Is
A lipoma is a benign growth of fat cells that forms just beneath the skin. It typically feels soft, doughy, and easily movable when you press on it — it tends to shift slightly under your fingers rather than staying fixed in place. Lipomas grow slowly, are usually painless, and can occur anywhere on the body, though the trunk, neck, and arms are common spots. Some people develop more than one over their lifetime, and there's often a genetic tendency toward them.
What a Cyst Is
The most common type, an epidermoid cyst, forms when skin cells and keratin get trapped beneath the surface, creating a firm, round sac. Cysts often have a small, darkened central pore (a punctum) visible on the surface — a helpful clue lipomas don't share. They tend to feel firmer and more clearly defined than lipomas, and while usually painless, they can become inflamed, tender, and infected, sometimes draining a thick, foul-smelling material if irritated or ruptured.
Key Differences at a Glance
| Feature | Lipoma | Cyst |
|---|---|---|
| Texture | Soft, doughy | Firmer, more defined |
| Mobility | Moves easily under the skin | Can be more fixed, attached to overlying skin |
| Central pore | Absent | Often present |
| Growth speed | Slow, over months to years | Can appear more suddenly, may fluctuate in size |
| Infection risk | Very low | Can become inflamed or infected |
Why the Distinction Matters for Treatment
Both lipomas and cysts are typically removed the same way — a straightforward in-office excision — if they're bothersome, growing, or in a spot that catches on clothing. Cysts specifically shouldn't be squeezed or "popped" at home, since this can push the contents deeper into the tissue and increase the risk of infection or scarring rather than actually resolving it.
Found a new lump you'd like checked?
Our board-certified dermatologists see patients at our Burien and Bellevue offices — same-week appointments are often available.
Schedule a Skin CheckWhen to See a Dermatologist
Most lumps under the skin are benign, but any lump that's hard, doesn't move under the skin, grows quickly, or is painful should be evaluated to rule out something less common. A cyst that becomes red, warm, and tender may be infected and needs treatment rather than home care.