Most cysts appear as round, smooth bumps under or on the skin, ranging from a tiny dot to several inches across. They’re usually flesh-colored or slightly yellow, feel firm to the touch, and move slightly when you press on them. But cysts show up in many different locations on the body, and each type has its own distinct look and feel.
Epidermoid Cysts: The Most Common Type
Epidermoid cysts (often mistakenly called sebaceous cysts) are the bumps most people picture when they think of a cyst. They appear as round, firm lumps just beneath the skin, typically on the face, neck, chest, or back. They range from as small as 1/16 of an inch to as large as four inches across, though most stay under an inch.
The signature feature is a tiny blackhead plugging the central opening of the cyst. This small dark dot at the top of the bump is a helpful clue that you’re looking at an epidermoid cyst rather than something else. The bump itself is usually flesh-colored or slightly yellowish and moves a bit when you push on it. Inside, it’s filled with a thick paste of dead skin cells, which is why these cysts sometimes produce a foul-smelling white or yellow discharge if they rupture.
Pilar Cysts on the Scalp
Pilar cysts grow almost exclusively on the scalp. They feel like smooth, flesh-colored lumps that you typically notice while washing or combing your hair. Unlike epidermoid cysts, pilar cysts don’t have a visible central pore. They’re round, dome-shaped, and can grow quite large over time. Because they sit on the scalp and match your skin color, they’re often easier to feel than to see.
Ganglion Cysts on Wrists and Hands
Ganglion cysts are fluid-filled lumps that most commonly appear on the back of the wrist, though they also develop at the base or end joint of a finger. They range from about a quarter inch to just over an inch across. One distinctive feature: they change size. Increased activity tends to make them swell, while rest shrinks them. They can appear quickly, disappear, and come back.
Because they’re filled with a thick, slippery joint fluid rather than solid material, ganglion cysts are somewhat translucent. A doctor can confirm this by shining a light through the bump. They feel firm but not rock-hard, and they don’t move around the way some other lumps do since they’re attached to a joint or tendon sheath underneath.
Baker’s Cysts Behind the Knee
A Baker’s cyst creates a visible bulge at the back of the knee, along with a feeling of tightness. It forms when excess joint fluid pushes into a pouch behind the knee. The swelling is often most noticeable when you’re standing. Pain tends to worsen with activity or when you fully straighten or bend the knee. Unlike skin cysts, a Baker’s cyst sits deep enough that you primarily see generalized swelling rather than a well-defined bump.
Eyelid Cysts vs. Styes
A chalazion is an eyelid cyst caused by a blocked oil gland. It shows up as a small, usually painless bump on the eyelid, typically farther back from the eyelid edge. It rarely makes the entire eyelid swell. It can become red and slightly tender, but it’s generally more of a nuisance than a source of real pain.
A stye, by contrast, looks like a red, painful pimple right at the base of an eyelash. Styes are infections, not cysts. They often produce a small pus spot at the center of the bump and can make the entire eyelid swell. If your eyelid lump is very painful and sits right at the lash line, it’s more likely a stye. If it’s deeper in the lid and not particularly sore, it’s probably a chalazion.
What an Infected Cyst Looks Like
An uninfected cyst is flesh-colored, painless or mildly tender, and sits quietly under the skin. When a cyst becomes infected, the changes are hard to miss. The skin around it turns red or darkens, the area swells noticeably, and the bump becomes painful to touch. You may also see yellow or greenish drainage, which often has a strong odor. A ruptured cyst looks similar: swelling, skin discoloration, pain, and a foul-smelling yellow fluid leaking from the area.
If a cyst that’s been stable for months or years suddenly becomes red, warm, and painful over a few days, infection or rupture is the most likely explanation.
How Cysts Differ From Lipomas
Lipomas are fatty lumps that people often confuse with cysts, but they feel quite different. A cyst is firm. A lipoma feels soft and doughy, almost rubbery. Lipomas slide easily under your finger when you press on them and are usually painless unless they happen to sit near a nerve. They’re typically under two inches across. Cysts tend to feel more fixed in place, firmer, and are more likely to become tender or inflamed over time. If the bump is squishy, painless, and moves freely, it’s more consistent with a lipoma than a cyst.
When a Lump Might Not Be a Cyst
Most cysts share a few reassuring features: they’re round or oval, symmetrical, smooth-edged, and uniform in color. The warning signs that a lump could be something more serious are essentially the opposite of those qualities. Irregular or uneven borders, variation in color across the surface, rapid growth compared to anything else on your skin, and a diameter larger than about 6 millimeters (roughly the size of a pencil eraser) are all reasons to have a lump evaluated. Any bump that bleeds easily from minor contact also warrants a closer look.
A cyst that has looked the same for years, feels smooth and round, and matches your skin color is very unlikely to be anything dangerous. A lump that’s new, growing noticeably, asymmetrical, or multicolored deserves professional attention regardless of whether you think it might be “just a cyst.”