Epidermoid Cyst: Symptoms, Causes, and Treatment

Epidermoid cysts are non-cancerous, balloon-like bumps that slowly develop under the skin. They are filled with keratin protein and can range in size from less than an inch to several inches wide. Some have a head in the center. Thick, yellow, foul-smelling liquid may drain out of the cyst.

Epidermoid cysts most often appear on the face, scalp, trunk, groin, and upper back, though they can pop up anywhere. They're typically harmless, but may require treatment if they become large, inflamed, and/or infected.

You should not attempt to drain or remove an epidermoid cyst yourself. When this is necessary, it should be done by a healthcare provider.

This article discusses epidermoid cysts and their appearance. It also looks at whether they cause health problems, how they are diagnosed, and the options for treatment.

Epidermoid Cyst Symptoms

A typical epidermoid cyst looks like a raised, round bump. You can usually feel the cyst wall when you touch it. You will probably be able to move the cyst around under the skin fairly easily.

There is often a small opening on the surface of the skin. It may look like a scab, but may be so small that it's hard to see. Other symptoms include:

• Pain at the lump site
• Inflammation or redness
• Yellow, cheesy, and thick fluid leaking from the cyst
• An unpleasant odor
  

When to See a Healthcare Provider

Small epidermoid cysts don't usually cause problems. But you should see a healthcare provider if your cyst is:

• Fast-growing
• Very large
• Painful
• Red or hot
• Broken (ruptured)
  

If the cyst wall ruptures, it exposes surrounding tissue to the keratin inside. This can cause irritation, pain, swelling, and increase your risk of infection.

Epidermoid Cyst Causes

Epidermoid cysts occur when epidermal cells—those that make up the outermost layer of skin, the epidermis—don't shed properly and move below the skin's surface. The cells become trapped and continue to grow. They also develop a "wall." The cyst wall is like a balloon that extends down into the dermis, the second layer of skin. The cells continue to make keratin, a protein found in skin, hair, and nails, which fills the cyst.

In some cases, a scrape or other type of injury are to blame. Surgery or body piercing can cause this as well.

Epidermoid cysts also may occur with rare genetic disorders like pachyonychia congenita.

Epidermoid cysts are the most common type of skin cyst.

Diagnosis

Epidermoid cysts account for the majority of skin cysts seen by skin specialists, so they can often be diagnosed by their appearance alone.

If needed, an in-office biopsy can be performed and reviewed by a pathologist. Under the microscope, the cells will look clumped, fibrous, and horn-like.Increasingly, the use of epidermoid cyst ultrasound will help a provider to arrive at a diagnosis.

In doing so, your healthcare provider may rule out other conditions through a differential diagnosis. Some possible causes that will need to be excluded are:

• Acne
• Sebaceous cyst
• Furuncle/boil
• Lipoma
• Milia
• Sebaceous hyperplasia

Epidermoid cysts also go by several other names. Your practitioner may use one of these when speaking to you about your diagnosis:

• Epidermal cyst
• Epidermal inclusion cyst
• Epithelial cyst
• Follicular infundibular cyst
• Infundibular cyst
  
• Keratin cyst

Treatment of an Epidermoid Cyst

An epidermoid cyst doesn't have to be treated if:

• It's small
• It doesn't hurt
• It's not red and swollen

If the cyst is inflamed or potentially infected, treatment may involve antibiotics or an injection with a corticosteroid (usually triamcinolone).

In other cases, a healthcare practitioner may want to drain the cyst. They may recommend using warm compresses for a few days to help the cyst continue to drain.

When an Epidermoid Cyst Has to Be Removed

Your healthcare provider may recommend removing your cyst if:

• It's in a place where it gets irritated. For example, it may rub against clothing or jewelry.
• It's getting larger quickly.
• It frequently gets inflamed or infected.

You may also request that a cyst be removed for cosmetic reasons.

To remove the cyst, your healthcare provider will make an incision and remove most of the contents. Then, your healthcare provider will separate the cyst wall from the surrounding tissue and remove it. If the incision is large, it may need to be stitched closed.

In doing this, the whole cyst wall is taken out. If the cyst is just drained but the cyst wall remains, it will start making more keratin. This will cause the cyst to return.

Summary

An epidermoid cyst is a common, benign cyst filled with keratin. Small cysts usually don't need to be treated.

Sometimes a cyst will grow very large or rupture. Inflamed cysts may be drained. Treatment can include warm compresses, antibiotics, or a corticosteroid injection.

You may want your cyst removed for cosmetic reasons, or because it is large or irritating. To remove the cyst, your healthcare provider will first drain it and then remove the cyst wall. Never attempt to remove an epidermoid cyst on your own.