Lumps Under The Skin: Cyst Vs Lipoma
Lumps Under The Skin: Cyst Vs Lipoma
A newly discovered lump beneath the skin can immediately trigger fear. Many people begin pressing it, squeezing it, searching online, and imagining the worst possible diagnosis before they have even spoken to a healthcare professional.
According to Dr. Armor, however, two of the most common explanations for a slow-growing lump under the skin are a lipoma or an epidermoid cyst. Both are usually benign, but they are formed from different materials, behave differently, and may require different approaches to treatment.
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“The first thing I tell patients is to stop squeezing the lump,” Dr. Armor said. “Repeatedly pressing it will not make a lipoma disappear, and attempting to pop a cyst can create inflammation, infection, and scar tissue.”
Although many lipomas and epidermoid cysts are harmless, Dr. Armor emphasized that no unexplained lump should be diagnosed solely through photographs, online descriptions, or self-examination. The NHS similarly advises that new lumps should be assessed by a medical professional, even when they appear consistent with a harmless lipoma.
Why These Two Lumps Are Frequently Confused
Lipomas and epidermoid cysts can both appear as rounded bumps beneath the skin. They may grow slowly, remain painless for years, and develop in areas such as the back, shoulders, neck, scalp, arms, thighs, or trunk.
To an untrained observer, they may look almost identical.
Dr. Armor explained that their internal structure is completely different.
A lipoma is a collection of mature fat cells growing beneath the skin. It is a solid fatty mass rather than a fluid-filled sac. An epidermoid cyst, by contrast, forms when skin cells and keratin accumulate inside a sac within the skin.
Keratin is the tough protein naturally found in skin, hair, and nails. When it becomes trapped inside a cyst, it may produce a thick, pale, paste-like substance that some people mistakenly describe as pus.
“People often call these sebaceous cysts,” Dr. Armor said. “But many of the common cysts we see are more accurately described as epidermoid or epidermal inclusion cysts. They contain keratin rather than simply being pockets of oil.”
The source material supplied for this report similarly describes lipomas as firm or rubbery collections of fat cells, while epidermoid cysts are described as sacs in the skin filled with keratin.
What a Lipoma Usually Feels Like
A typical lipoma develops below the surface of the skin and usually feels soft, doughy, or rubbery.
One of its most recognizable features is mobility. When pressed gently, it may shift slightly beneath the fingers instead of feeling firmly attached to the skin above it.
“The skin over a lipoma usually looks completely normal,” Dr. Armor explained. “You generally do not see a pore, a black dot, drainage, or a visible opening.”
Most lipomas are painless. However, discomfort can occur if a growing lipoma presses against a nerve, lies near a joint, or develops in an area exposed to repeated pressure.
Lipomas can vary considerably in size. Some are barely noticeable, while others grow large enough to affect clothing, movement, or physical appearance.
They most commonly appear during middle age, although they can develop at almost any stage of life. Some people develop only one, while others may experience several over time.
According to Dr. Armor, having a lipoma does not necessarily mean someone is unhealthy or has consumed too much fat.
“A lipoma is not simply excess body fat collecting in one spot,” he said. “Thin people can develop them, and people living with obesity may never develop one.”
Researchers do not always know exactly why a particular lipoma appears. Family tendency may play a role in some cases, and certain uncommon inherited conditions may be associated with multiple fatty growths.
What an Epidermoid Cyst Usually Looks Like
An epidermoid cyst often sits closer to the surface of the skin than a lipoma.
Rather than moving freely underneath the skin, it may feel attached or fixed because the cyst wall is located within the skin itself.
A small dark opening, medically known as a punctum, may be visible on the surface. This can resemble a large blackhead or blocked pore.
“That central opening is one of the most helpful clues,” Dr. Armor said. “A lipoma does not usually have a visible pore. A cyst often does.”
Epidermoid cysts are frequently flesh-colored or slightly yellowish. They may remain small for a long time, or gradually enlarge as additional keratin accumulates inside the sac.
When pressed, some cysts release thick, white or yellow material with a strong odor. Although squeezing may temporarily reduce the size of the bump, it does not remove the cyst wall.
As long as that wall remains beneath the skin, the cyst can fill again.
Mayo Clinic notes that simple drainage can relieve symptoms but may allow the cyst to return because the entire cyst structure has not necessarily been removed.
The Critical Difference: Cysts Can Rupture
One of the clearest differences between a lipoma and an epidermoid cyst is their reaction to pressure.
A lipoma is a solid mass of fatty tissue. It does not normally rupture or release material through the surface.
An epidermoid cyst, however, can break open.
Rupture may happen naturally as the cyst enlarges, or it may occur after repeated squeezing, scratching, or attempts to puncture it at home.
“When the cyst wall ruptures, keratin escapes into the surrounding tissue,” Dr. Armor explained. “The immune system reacts strongly because that material is now outside the sac where it belongs.”
The result may be sudden redness, swelling, tenderness, warmth, and significant inflammation. A ruptured cyst may resemble an abscess, even when bacteria are not initially responsible for the reaction.
Bacteria can later enter the damaged area and produce a secondary infection.
Dr. Armor warned that inflammation and scarring may also make future surgical removal more difficult.
“A calm, intact cyst is generally easier to remove than one that has repeatedly ruptured and healed with scar tissue,” he said. “This is why squeezing is not a harmless habit.”
Should a Lipoma Be Removed?
In many cases, a confirmed lipoma does not need treatment.
A person may choose observation when the growth is small, painless, stable, and not interfering with movement or appearance. Lipomas are generally harmless and often require no treatment, according to NHS guidance.
Removal may be considered when the lipoma becomes painful, grows noticeably, presses on nearby structures, restricts movement, or causes significant cosmetic concern.
Surgical excision is the most direct treatment. During the procedure, a healthcare professional removes the fatty mass through an incision, usually under local anesthesia when the lipoma is small and accessible.
Dr. Armor described it as a relatively straightforward outpatient procedure in many cases.
“When the entire lipoma is removed, recurrence in that exact location is uncommon,” he said. “But removing one does not prevent another lipoma from developing somewhere else.”
A doctor may recommend imaging or further testing if the lump is unusually deep, firm, rapidly growing, painful, attached to deeper tissue, or otherwise inconsistent with a typical lipoma.
When an Epidermoid Cyst Needs Treatment
Like lipomas, small epidermoid cysts may sometimes be left alone.
If the cyst is not painful, inflamed, infected, or cosmetically troubling, observation may be reasonable after a medical professional confirms the diagnosis. Mayo Clinic states that an epidermoid cyst can often be left untreated when it is not painful or bothersome.
Treatment becomes more likely when the cyst repeatedly swells, ruptures, drains, becomes painful, catches on clothing, or grows large enough to create pressure.
A healthcare professional may use anti-inflammatory treatment for a swollen cyst. If an abscess or bacterial infection is present, drainage or medication may be necessary.
However, Dr. Armor stressed that draining the contents is not the same as permanently removing the cyst.
“For definitive treatment, the complete cyst wall generally needs to be removed,” he said. “If part of that wall is left behind, the cyst may return.”
Surgical removal is often delayed until severe inflammation has settled because an acutely swollen cyst can be more difficult to excise completely.
Why Home Popping Is a Bad Idea
Social media videos may make cyst extraction appear simple, but Dr. Armor warned that at-home popping carries real risks.
Unsterile needles, blades, or squeezing tools can introduce bacteria into the skin. Excessive pressure can push cyst contents deeper into surrounding tissue rather than bringing them safely to the surface.
Potential consequences include infection, bleeding, inflammation, permanent scarring, discoloration, and recurrence.
Attempting to squeeze a suspected lipoma is equally unhelpful because there is no material that can be expressed through the skin.
“You cannot push a lipoma out through a pore,” Dr. Armor said. “There is no opening and no liquid center. Continued manipulation only irritates the surrounding tissue.”
Warning Signs That Require Medical Attention
Dr. Armor cautioned that not every lump under the skin is a cyst or lipoma.
A medical examination is particularly important when a lump grows quickly, becomes hard, feels fixed to deeper structures, appears irregular, causes persistent pain, bleeds, ulcerates, or returns after removal.
Other concerning signs include fever, spreading redness, significant warmth, pus-like drainage, or red streaks extending away from the area.
Lumps located in the breast, testicle, neck, armpit, groin, abdomen, or near major joints should not automatically be assumed to be simple skin growths.
“Most lumps are not emergencies, but appearance alone is not always enough,” Dr. Armor said. “The responsible approach is to have a professional examine anything new, changing, or unusual.”
A clinician may diagnose a typical superficial lipoma or cyst through physical examination. In less clear cases, ultrasound, biopsy, or other imaging may be considered to determine whether the mass is solid, cystic, deep, or connected to nearby structures. Dermatology guidance recognizes imaging, including ultrasound, as useful when the nature of a skin lesion is uncertain.
Dr. Armor’s Simple Comparison
Dr. Armor offered a practical summary for people trying to understand the basic differences.
A lipoma usually feels soft or rubbery, sits beneath normal-looking skin, moves slightly when pressed, contains fatty tissue, and does not rupture.
An epidermoid cyst usually sits within or close to the skin, may feel more fixed, can have a visible central pore, contains keratin, may drain unpleasant-smelling material, and can rupture or become inflamed.
These signs can provide useful clues, but they cannot establish a diagnosis with complete certainty.
The Bottom Line
Discovering a lump under the skin can be frightening, but panic and repeated squeezing are rarely helpful.
Lipomas and epidermoid cysts are common and usually benign. Many can be safely monitored, while others can be treated with relatively minor procedures when they cause pain, inflammation, repeated drainage, restricted movement, or cosmetic distress.
The most important distinction is that a lipoma is a solid fatty growth beneath the skin, while an epidermoid cyst is a keratin-filled sac located within the skin.
Dr. Armor’s final message is straightforward.
“Do not allow an online search to convince you that every lump is deadly, but do not diagnose it entirely by yourself either,” he said. “Leave it alone, watch for changes, and let a qualified healthcare professional examine it. Most of the time, the answer is far less frightening than the fear created by uncertainty.”