Is That Lump Growing? Why Epidermoid Cysts Form & Medical Next Steps

Finding a new lump under your skin can be unsettling. If it feels smooth, round, and slowly growing, one common cause is an epidermoid cyst. These cysts are usually harmless, but understanding why they form — and when to seek medical care — can help you make informed, confident decisions.

Below, we'll explain what an epidermoid cyst is, why it may grow, when to see a doctor, and what treatment options are available.

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What Is an Epidermoid Cyst?

An epidermoid cyst is a small, slow-growing lump that forms beneath the skin. It develops when skin cells (called keratin-producing cells) move deeper into the skin instead of shedding off the surface as they normally would.

These trapped cells continue producing keratin, a soft, protein-like material. Over time, keratin builds up inside a thin sac, forming a cyst.

Common characteristics of an epidermoid cyst:

• Round or dome-shaped lump under the skin
• Usually skin-colored, white, or yellowish
• Often has a small dark center (a clogged pore)
• Moves slightly when touched
• Typically painless unless inflamed or infected
• Grows slowly over months or years

Epidermoid cysts can appear anywhere, but they are most common on the:

• Face
• Neck
• Chest
• Upper back
• Genitals

They are very common in adults and can occur in both men and women.

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Why Do Epidermoid Cysts Form?

Epidermoid cysts develop when skin cells become trapped beneath the surface. Several factors may increase your risk:

1. Blocked Hair Follicles or Pores

A clogged pore or hair follicle can trap skin cells underneath the surface.

2. Skin Injury

Cuts, surgical wounds, acne, or other skin damage can push surface skin cells deeper into the skin, where they continue growing.

3. Acne or Oily Skin

People prone to acne may be more likely to develop epidermoid cysts.

4. Genetic Conditions (Rare)

Certain rare inherited disorders can increase the number of cysts, but this is uncommon.

In most cases, there's no serious underlying cause. Epidermoid cysts are usually benign (non-cancerous).

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Is It Normal for an Epidermoid Cyst to Grow?

Yes — slow growth is typical.

Because the cyst sac continues producing keratin, it may gradually increase in size. Some cysts remain small for years. Others may grow to several centimeters across.

However, growth can happen for different reasons:

Normal Growth:

• Slow enlargement over months or years
• No pain
• No redness

Concerning Changes:

• Rapid swelling
• Increasing pain
• Redness or warmth
• Drainage of foul-smelling material
• Fever

Sudden changes often signal inflammation or infection, not cancer — but they do require medical evaluation.

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Can an Epidermoid Cyst Become Cancer?

This is rare.

The vast majority of epidermoid cysts are benign. Very rarely, skin cancers such as squamous cell carcinoma can arise within a cyst. Warning signs that require medical evaluation include:

• Rapid, unexplained growth
• Firmness that feels different from before
• Ulceration (open sore)
• Persistent bleeding
• Changes in color

While this is uncommon, it's important not to ignore suspicious changes. If you're concerned about your symptoms and want to understand whether they match the typical presentation of an Epidermoid Cyst, a free AI-powered symptom checker can help you determine whether medical evaluation is warranted.

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Should You Squeeze an Epidermoid Cyst?

No.

It may be tempting, especially if there's a visible opening. But squeezing a cyst can:

• Push material deeper into the skin
• Cause inflammation
• Increase risk of infection
• Lead to scarring
• Make future removal more difficult

If the cyst ruptures under the skin, it can become painful and swollen. Medical treatment is safer and more effective.

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When Should You See a Doctor?

Most epidermoid cysts are not emergencies. However, you should schedule a medical appointment if:

• The cyst becomes painful
• It grows quickly
• It becomes red, warm, or swollen
• It starts draining pus
• It interferes with movement or daily activities
• It causes cosmetic concerns
• You are unsure whether it is truly an epidermoid cyst

You should seek urgent medical care if you develop:

• Fever
• Spreading redness
• Severe pain
• Signs of a deep infection

Any lump that changes rapidly or looks unusual should be evaluated by a healthcare professional.

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How Is an Epidermoid Cyst Diagnosed?

Doctors usually diagnose an epidermoid cyst by examining the skin. In most cases:

• No imaging is needed
• No lab tests are required

If the cyst looks unusual, your doctor may:

• Order imaging (such as ultrasound)
• Perform a biopsy
• Remove it and send it for laboratory testing

These steps help rule out other conditions if there is any uncertainty.

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Treatment Options for an Epidermoid Cyst

Not all cysts require treatment. If the cyst is small and not bothersome, your doctor may recommend simply monitoring it.

Treatment options include:

1. Observation

If the cyst is painless and stable, no treatment may be necessary.

2. Steroid Injection

If inflamed but not infected, a corticosteroid injection can reduce swelling.

3. Incision and Drainage

If infected, the doctor may:

• Open the cyst
• Drain the contents
• Prescribe antibiotics (if needed)

However, this does not remove the cyst sac, so it may return.

4. Surgical Removal (Definitive Treatment)

The most effective treatment is minor surgical removal. The doctor:

• Makes a small incision
• Removes the entire cyst sac
• Closes the skin

This reduces the chance of recurrence. The procedure is usually quick and done under local anesthesia.

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Will an Epidermoid Cyst Go Away on Its Own?

Most epidermoid cysts do not completely disappear without treatment. Some may shrink temporarily, especially if they rupture and drain. However, if the cyst wall remains, it can refill.

That said, many cysts remain stable and never cause problems.

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Can You Prevent Epidermoid Cysts?

There is no guaranteed way to prevent them. However, general skin care may help reduce risk:

• Treat acne early
• Avoid picking or squeezing skin lesions
• Keep skin clean
• Manage oily skin if prone to breakouts

Even with good skin care, some cysts still form.

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What Else Could That Lump Be?

Not every lump is an epidermoid cyst. Other possibilities include:

• Lipoma (fatty tumor)
• Abscess
• Swollen lymph node
• Pilar cyst
• Skin cancer

This is why medical evaluation is important if you're unsure.

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The Bottom Line

An epidermoid cyst is a common, usually harmless lump under the skin. Slow growth is typical and does not automatically signal danger. However, rapid changes, pain, redness, or drainage require medical attention.

Most cysts:

• Are benign
• Grow slowly
• Can be safely removed if needed
• Do not pose serious health risks

Still, no online information can replace personalized medical care. If you notice a new lump, a change in an existing cyst, or any concerning symptoms, speak to a doctor. Some skin changes can signal more serious conditions, and only a healthcare professional can properly evaluate and diagnose them.

If you're experiencing symptoms and want guidance on your next steps, checking your symptoms with a free Epidermoid Cyst assessment tool can provide clarity before your doctor's visit — helping you arrive prepared with the right questions and information.

When it comes to lumps under the skin, it's always better to check than to guess.