Lipoma vs. Sebaceous Cyst

A soft lump under the skin is a soft lump under the skin — until you start trying to figure out what kind. Two of the most common culprits are lipomas and sebaceous cysts. They can look similar from the outside, but they’re different structures with different causes and sometimes different treatment needs.

Here’s how to tell them apart.

What Is a Sebaceous Cyst?

A sebaceous cyst (also called an epidermoid cyst) forms when the outer layer of skin, or the sac around a hair follicle, grows inward and fills with keratin — a protein naturally produced by skin cells. The result is a round, enclosed sac sitting just under the skin’s surface.

Unlike a lipoma, a cyst often has a visible punctum (a small dark dot) at the surface, may occasionally drain a white or foul-smelling material, and can become inflamed or tender, especially if it gets infected. Cysts are also very common and usually benign, but they can become problematic if they rupture or get infected.

What Is a Lipoma?

A lipoma is a benign growth made of fat cells, nestled in the tissue layer between skin and muscle. Unlike cysts, lipomas have no connection to the skin surface — they’re entirely enclosed in their own capsule.

Lipomas tend to feel soft, doughy, and distinctly movable. They have no skin attachment or visible opening, cause little to no pain in most cases, and grow slowly over months or years.

How to Tell Them Apart

Texture: Lipomas are typically soft and uniform. Cysts can feel slightly firmer or rubbery and may feel tense if there’s internal pressure building up.

Skin surface: Cysts often have a small punctum — a tiny dark dot — where the sac connects to the skin surface. Lipomas have no skin connection at all.

Tenderness: A simple lipoma is almost never tender. Cysts, especially inflamed or infected ones, can be quite painful and swollen.

Depth: Lipomas tend to sit in deeper soft tissue. Cysts are almost always right under the surface of the skin.

Odor if pressed: Cysts may produce a characteristic odor if material is expressed. Lipomas produce nothing.

Can You Tell for Sure Without a Doctor?

Honestly, it can be hard to distinguish between the two on your own — especially for lumps that fall outside the typical pattern. Some lipomas are firm, and some cysts are soft. A physician who examines the lump can give you a clear answer. Imaging is sometimes used to confirm the diagnosis when there’s uncertainty.

If you have a lump that’s been growing, changing, becoming tender, or just doesn’t seem right to you, it’s worth getting it looked at. The good news is that both conditions are usually very treatable.

How Are They Treated?

Lipoma removal: Dr. Ash performs lipoma excisions in-office under local anesthesia. A small incision is made, the lipoma and its capsule are removed, and the incision is closed. Most patients return to normal activity within a day or two.

Cyst removal: Sebaceous cysts can often be removed in-office as well. Complete excision of the cyst wall is important to prevent recurrence. An infected cyst may need to be drained first, with full removal scheduled once the inflammation has settled.

Neither procedure requires general anesthesia or a hospital stay for most patients.