Most bumps you can feel under your skin are benign. Lipomas, cysts, swollen lymph nodes, and ganglion cysts account for the vast majority of subcutaneous lumps in adults. While finding an unexpected bump can be alarming, understanding what different types feel like can help you figure out what you’re dealing with and whether it needs attention.
Lipomas: Soft, Movable, and Painless
Lipomas are one of the most common reasons people feel a bump under the skin. These are slow-growing collections of fat cells that sit between your skin and the muscle layer beneath it. They feel soft and doughy, almost like a small rubber ball, and they move easily when you press on them. Most are painless and stay under 2 inches in diameter, though they can occasionally grow larger.
Lipomas can show up almost anywhere on the body but are especially common on the neck, shoulders, back, abdomen, arms, and thighs. They tend to appear in middle age and sometimes run in families. A single lipoma rarely causes problems unless it presses on a nerve, which can make it tender. Many people have more than one.
Cysts: Firm, Tender, and Sometimes Inflamed
If the bump feels firm rather than soft, it may be a cyst. Epidermoid cysts (sometimes called sebaceous cysts) form when skin cells get trapped beneath the surface and build up inside a sac. They often feel like a small marble under the skin, and unlike lipomas, they’re typically firmer, can be tender to the touch, and may develop redness or swelling around them.
Cysts sometimes have a small dark opening (a punctum) on the skin’s surface. They can stay the same size for years or slowly enlarge. If a cyst ruptures or becomes infected, it turns painful quickly, and the surrounding skin may become red and warm. Infected cysts sometimes drain thick, foul-smelling material. Uninfected cysts are usually left alone unless they bother you cosmetically or keep getting inflamed.
Swollen Lymph Nodes
If the bumps you’re feeling are in your neck, armpits, or groin, there’s a good chance they’re lymph nodes. Lymph nodes are small, bean-shaped structures that filter fluid and trap bacteria and viruses. You have hundreds of them throughout your body, but you can only feel them in a few locations: the neck, under the jaw, behind the ears, the armpits, the chest, the abdomen, and the groin.
Upper respiratory infections are the leading cause of swollen lymph nodes. Colds, the flu, sinus infections, strep throat, and minor skin infections all trigger your lymph nodes to enlarge as they ramp up immune activity. A swollen node from an infection typically feels like a tender, rubbery bump roughly the size of a pea or grape. It usually shrinks back to normal within two to four weeks after the infection clears.
Less commonly, persistent swollen lymph nodes can be associated with autoimmune conditions like lupus or rheumatoid arthritis, certain viral diseases like hepatitis or shingles, reactions to medications, or cancers. The key distinction is timing: nodes that swell during an obvious illness and resolve afterward are rarely concerning. Nodes that grow steadily over weeks without an obvious cause, feel hard or fixed in place, or appear in multiple areas at once deserve a closer look.
Ganglion Cysts Near Joints
Bumps near your wrist, hand, ankle, or foot are frequently ganglion cysts. These round or oval lumps grow out of the lining of a joint or tendon and are filled with a thick, jellylike fluid similar to the lubricating fluid found inside joints. They look and feel like a tiny water balloon on a stalk, and they can range from pea-sized to about an inch across.
Ganglion cysts often change size. They may swell with repetitive motion or joint use and shrink during rest. Some are painless, while others cause a dull ache or sharp pain if they press on a nearby nerve. They’re not cancerous and sometimes disappear on their own. If one causes persistent pain or interferes with movement, a doctor can drain it or recommend removal.
Dermatofibromas and Other Skin Growths
Some bumps under the skin are actually firm growths within the skin itself. Dermatofibromas are small, hard nodules typically 0.5 to 1 centimeter across. They’re made of fibrous tissue, feel like a small bead embedded in the skin, and are usually red to brown in color (they can appear darker on deeper skin tones). One distinctive feature: if you pinch the skin around a dermatofibroma from the sides, it dimples inward rather than popping outward. They’re harmless and don’t require treatment unless they’re irritating.
Cherry angiomas are another possibility, especially after age 30. These are clusters of tiny blood vessels that form small, raised, bright red bumps on the skin’s surface. They’re completely benign and extremely common as people age.
Boils and Abscesses
If the bump appeared quickly, is painful, warm, and getting bigger, it may be a boil or abscess. These are localized infections where bacteria (often staph) enter through a hair follicle or small skin break and create a pocket of pus beneath the skin. An abscess is generally larger and deeper than a boil, with significant redness and swelling over the area.
When the infection spreads into the surrounding skin rather than staying contained in one pocket, it becomes cellulitis. The hallmarks of cellulitis are spreading redness, skin that’s warm and tender over a widening area, and sometimes fever. Cellulitis can expand quickly and needs prompt treatment with antibiotics, while a contained abscess often needs to be drained.
How Doctors Evaluate a Bump
For most subcutaneous lumps, a physical exam is enough to reach a diagnosis. Your doctor will assess how the bump feels, whether it moves, where it is, and how long it’s been there. When the diagnosis isn’t clear from touch alone, ultrasound is typically the first imaging tool used for superficial, palpable lumps. It’s quick, painless, and effective at distinguishing fluid-filled cysts from solid masses. In some cases, a standard X-ray is also useful, since it can reveal calcification within a mass, bone involvement, or fat content that points to a specific diagnosis.
If imaging raises questions, a biopsy may follow. The most common approach for skin and subcutaneous lumps is a punch biopsy, which uses a small cylindrical tool (a few millimeters wide) to take a core sample of tissue deep enough to include the fat layer beneath the skin. The area is numbed with local anesthetic, and the procedure takes just a few minutes. For bumps that sit entirely on the skin’s surface, a shave biopsy, which removes a thin horizontal slice, may be sufficient.
Signs a Bump Needs Attention
The vast majority of soft tissue lumps in adults are benign. Still, certain features should prompt you to get a bump evaluated sooner rather than later:
- Size over 5 centimeters (roughly 2 inches), or rapid growth over weeks
- Hard and fixed in place, not movable under the skin
- Pain that worsens without an obvious cause like infection or injury
- Skin changes overhead, such as ulceration that doesn’t heal within a week or two
- Location deep to muscle, which you might notice as a firm lump that doesn’t move with the skin above it
- Accompanying symptoms like unexplained weight loss, night sweats, or fever
In children, subcutaneous masses warrant closer evaluation in general, since a higher percentage of soft tissue masses in children turn out to be malignant compared to adults. For adults, the odds are strongly in your favor that what you’re feeling is something entirely harmless.