Most cysts announce themselves as a small, firm lump you can feel under your skin or through symptoms like pressure, pain, or swelling in a specific area. Some cysts, though, produce no symptoms at all and are only discovered during imaging for something else entirely. How you’ll know depends largely on where the cyst forms: near the surface of your skin, inside a joint, or deep within an organ like an ovary or kidney.
What a Cyst Feels Like Under the Skin
Skin cysts are the easiest to detect on your own. They’re round, sometimes dome-shaped bumps sitting just beneath the skin surface. They can appear yellow, pale, or skin-colored, and they range from smaller than a pea to several centimeters across. Many have a smooth surface and move slightly when you press on them, which helps distinguish them from structures that are fixed to deeper tissue.
Some skin cysts have a small central opening called a punctum, a tiny dot connecting the cyst to the skin surface. This is one of the more reliable visual clues. Skin cysts typically grow slowly over weeks or months and are painless unless they become infected. When infection sets in, the cyst turns red, swollen, and tender, and it may drain thick, foul-smelling material.
Ganglion Cysts on Wrists and Joints
Ganglion cysts develop along tendons or joints, most commonly on the wrists and hands, followed by ankles and feet. They’re filled with a jellylike fluid and typically measure 1 to 2 centimeters across, though some start as small as a pea. When you press on one, it feels like a firm rubber ball tethered in place by its attachment to the underlying joint.
These cysts often change size over time, growing larger with repeated joint movement and sometimes shrinking or disappearing on their own. You might notice decreased grip strength, reduced range of motion, or an aching discomfort near the affected joint. Some ganglion cysts are too small to feel and only cause a vague sense of something being “off” during certain movements.
Baker’s Cysts Behind the Knee
A Baker’s cyst forms as a fluid-filled sac behind the knee, and it often feels like tightness or a dull ache in that area. The swelling is most visible when you’re standing with your leg fully extended and tends to shrink when you bend your knee to about 45 degrees. Pain typically worsens with activity and can limit how far you bend or straighten the knee.
In adults, Baker’s cysts rarely appear out of nowhere. They’re usually linked to an underlying knee problem like a meniscal tear, osteoarthritis, or rheumatoid arthritis. The cyst forms because excess joint fluid gets pushed into a pocket behind the knee. If a Baker’s cyst ruptures, it can cause sudden sharp pain in the knee and calf, calf swelling, and a distinctive sensation of water running down the back of your lower leg. This can mimic a blood clot, so it’s worth getting checked promptly.
Ovarian Cysts and Pelvic Symptoms
Ovarian cysts are among the most common internal cysts, and most form as a normal part of the menstrual cycle. These functional cysts develop when a follicle either fails to release its egg or when the structure left behind after ovulation seals shut and fills with fluid. They’re usually harmless, rarely cause pain, and often disappear on their own within two to three menstrual cycles.
When an ovarian cyst does produce symptoms, the hallmark is pelvic pain on one side, below the bellybutton. It may feel like a dull ache that comes and goes or a sharper, more localized pain. You might also notice bloating, a feeling of fullness or heaviness in the lower abdomen, or pain during certain activities. Sudden, severe pelvic or abdominal pain is a red flag that could signal a ruptured cyst or ovarian torsion (when the ovary twists on itself), both of which need immediate medical attention.
Signs a Cyst May Be Infected
An infected cyst behaves differently from a calm one. The area becomes red, warm, swollen, and painful to touch. You might develop a fever, chills, fatigue, or a reduced appetite. If the cyst drains on its own, the discharge is often thick and foul-smelling.
An infected cyst can progress into an abscess, which is a walled-off pocket of pus caused by bacterial infection. The pus is highly contagious, so avoid squeezing or popping it yourself. Abscesses generally need to be drained by a healthcare provider, sometimes with a course of antibiotics.
How Doctors Confirm a Cyst
If you find a lump or have persistent symptoms, the first step is usually a physical exam. For lumps near the skin’s surface, a doctor can often tell by feel whether it’s likely a cyst, but imaging confirms it. Ultrasound is the most common tool because it clearly shows whether a mass is filled with fluid (a cyst) or is solid. Fluid-filled structures and solid masses transmit sound waves at different speeds, and ultrasound can distinguish between the two with high accuracy.
For internal cysts, like those on the ovaries, kidneys, or liver, ultrasound or CT scans are standard. If a cyst has unusual features, such as thick walls, internal divisions, or solid components mixed with fluid, your doctor may recommend further imaging or a fine needle aspiration. This procedure uses a thin needle to withdraw a small sample of fluid or tissue from the cyst. It helps determine what’s inside and can rule out more serious conditions.
Cyst vs. Tumor: Key Differences
The word “cyst” can sound alarming, but the vast majority of cysts are benign. The critical difference is that a cyst is a sac filled with fluid, air, or semi-solid material, while a tumor is a solid mass of tissue. On ultrasound, this distinction is usually clear. A simple, fluid-filled cyst with thin walls and no solid components is almost always noncancerous.
Characteristics that warrant prompt evaluation include a mass that grows rapidly, changes color, looks red or inflamed, bleeds, causes significant pain, or interferes with daily activities. Hard, fixed lumps that don’t move under pressure are also more concerning than soft, mobile ones. None of these features automatically mean cancer, but they’re reasons to get a professional assessment sooner rather than later.
Cysts That Need No Treatment
Many cysts resolve without any intervention. Functional ovarian cysts disappear within a few menstrual cycles. Ganglion cysts frequently shrink and sometimes vanish entirely. Small skin cysts that aren’t bothering you can simply be monitored over time.
Treatment is typically considered when a cyst causes pain, limits movement, becomes infected, keeps growing, or sits in a cosmetically sensitive area. Options range from draining the cyst with a needle to surgical removal, depending on the type, location, and whether it’s likely to come back. Cysts that are drained but not fully removed do have a tendency to refill, so complete removal is sometimes the better long-term option for recurring ones.