A cyst under the skin typically feels like a firm, round lump that you can move slightly with your fingers. Most are about the size of a pea to a marble, though they can grow larger. Unlike a pimple or a swollen lymph node, a cyst has a distinct, self-contained quality to it, almost like a small ball sitting just beneath the surface.
How a Typical Cyst Feels
The most common cysts people find under their skin are epidermoid cysts (often called sebaceous cysts, though that’s technically a misnomer). When you press on one, it feels firm but not rock-hard. It has some give to it, like pressing on a grape. The surface is smooth, and the lump sits just under the top layer of skin, so you can usually slide the skin over it or nudge the whole bump side to side slightly.
Most are round or dome-shaped. Some have a tiny dark dot in the center, which is a small opening connecting the cyst to the skin’s surface. They range from 1 to 2 millimeters (barely noticeable) up to 5 centimeters or more, with the average being about 2 centimeters across. They grow slowly, often over months or years, so you might notice one day that a bump you’ve had for a while has gotten a bit bigger.
When a cyst is healthy and uninfected, it’s usually painless. You might forget it’s there until you happen to touch it. It won’t feel warm, and the skin over it looks normal or slightly yellowish.
Where They Usually Show Up
Epidermoid cysts appear most often on the face, neck, chest, upper back, and sometimes the groin area. Pilar cysts, which feel very similar, tend to show up on the scalp. Scalp cysts can catch on a comb or brush, which is often how people first notice them. Both types feel like smooth lumps just under the skin surface and behave the same way when you touch them.
How a Cyst Feels Different From a Lipoma
People often confuse cysts with lipomas, but they feel noticeably different. A lipoma is a growth of fatty tissue that sits between muscle and skin. It feels soft and doughy, almost like a piece of rubber you can squish easily. A cyst feels firmer and more defined, with clearer edges. Think of the difference between pressing on a marshmallow (lipoma) and pressing on a grape (cyst).
Lipomas also tend to sit a bit deeper than cysts. A cyst feels like it’s right at the surface, while a lipoma can feel embedded in the tissue underneath. Both move when you push on them, but a cyst has a more distinct, ball-like shape under your fingertip.
What Changes When a Cyst Gets Infected
An infected or inflamed cyst feels very different from a calm one. The most obvious change is pain. What was previously painless becomes tender, sometimes significantly so. The area around the cyst swells, and the skin over it may turn red or change color. It often feels warm to the touch.
An inflamed cyst can swell to several times its original size over just a few days. It may start to feel softer and more pressurized as fluid builds up inside. In some cases, the cyst ruptures and drains a thick, cheese-like material that has a strong, unpleasant smell. A cyst that breaks open can develop a deeper infection, so rapid swelling, increasing pain, or drainage are signs worth getting checked.
It’s worth noting that cysts can become inflamed and swollen even without a true bacterial infection. Your body sometimes reacts to the cyst’s contents on its own, producing redness and tenderness that looks identical to an infection from the outside.
When a Lump Doesn’t Feel Like a Cyst
Certain characteristics suggest a lump is something other than a benign cyst. A growth that feels fixed in place and doesn’t slide under the skin at all is less typical of a cyst. Irregular edges, where the border of the lump feels ragged or uneven rather than smooth and round, also warrant attention.
Skin cancers can sometimes appear as lumps, but they tend to feel and look quite different. Basal cell carcinoma often presents as a pearly or waxy bump, sometimes with a sore that won’t heal. Squamous cell carcinoma can feel like a firm, rough nodule with scaly or crusty skin and irregular borders. Melanoma typically involves changes in color, with uneven edges and an evolving appearance. None of these feel like the smooth, mobile, well-defined ball of a cyst.
A lump that grows rapidly over weeks, feels hard and immovable, bleeds, or develops a crusty surface is worth having evaluated. A simple cyst, by contrast, grows slowly, moves freely, has smooth borders, and sits just under the surface like a small marble you can roll between your fingers.