Epidermal Cyst

Epidermal Cyst

What is an epidermal cyst?

An epidermal cyst is a non-cancerous superficial skin mass caused by implantation of the epidermal elements into the dermis.   Epidermis is the surface layer of skin while the dermis is the deeper layer.  It presents as a mass underneath the epidermal layer of the skin.  The mass is formed by a collection of greasy or cheesy dirty white substances contained in a sac or surrounded by a capsule.  Oftentimes, there is a punctum or opening seen on the skin surface over the sac.




The mass is formed by a collection of greasy or cheesy dirty white substances contained in a sac or surrounded by a capsule. 

Epidermal cysts are the most common skin masses.  They can occur in practically any part of the body that is covered by skin.  They can be of any size at time of detection.

There is no known way of prevention.

How to recognize an epidermal cyst?

The pattern recognition indicators are: superficial skin mass with a punctum.  The accuracy rate of these pattern recognition indicators for epidermal cyst is 99%.   In the presence of these pattern recognition indicators, there is no need for further diagnostic tests.


What is the difference between sebaceous cyst and epidermal cyst?

Strictly speaking, they are the same as the term “sebaceous cyst” has been found to be a misnomer. Initially, it was thought that the greasy or cheesy dirty white substance within the cyst is a sebaceous material.  It was later discovered that it is a keratinous material coming from the epidermis of the skin.  Thus, the accepted term nowadays is epidermal cyst.

How should an epidermal cyst be managed?

First, make sure it is an epidermal cyst using the pattern recognition indicators.

Second, if it is 99% epidermal cyst, do not worry on the 1% it being a skin cancer.

Third, for non-inflamed or infected epidermal cysts, use the size and the location factors to make a decision on what to do, either wait and watch or have it removed.

As a general guide, if the size is 1-cm or less in its greatest diameter and is located in a non-conspicuous part of the body, wait and watch.

If the epidermal cyst is more than 1-cm in its greatest diameter and is growing bigger, have it removed.  Infection is a potential complication of big epidermal cysts and it is harder to remove when the cyst is infected or has been infected.

Fourth, for epidermal cysts with history of inflammation or infection and which subside with antibiotics, have them removed while there is no acute bout of inflammation yet.

Fifth, for mildly inflamed epidermal cysts, take antibiotics and wait and watch. If inflammation subsides, have them removed 4 to 6 weeks after.  If inflammation progresses, have an incision and drainage done.

Sixth, for moderately to severely inflamed and infected epidermal cysts, have an incision and drainage done.  Recurrence is high as usually the entire sac or capsule cannot be removed totally when there is inflammation.   If the epidermal cysts recurred, have them removed at the time the inflammation has completely subsided.

How is an epidermal cyst removed or operated on?

The type of operations depends on the status of the epidermal cysts, whether inflamed or infected or not; whether not operated before or recurrent one; and whether there is a thinned-out overlying skin or not secondary to the size and duration.

There are basically three types of operations being done for epidermal cysts.  One is the conventional wide excision; second is the minimal incision-surgery; and third, incision and drainage (and curettage) for the inflamed or infected ones.

For the non-inflamed or infected epidermal cysts, the options are conventional wide excision and minimal incision-surgery.  Whatever option is taken, the goal is complete removal of the cyst together with the sac to avoid a recurrence.

Usually, for recurrent ones and those with thinned-out overlying skin, the conventional wide excision is done.

For the non-recurrent ones and those with non-thinning of the overlying skin, the options are the conventional wide excision and minimal incision-surgery.

In the conventional wide excision, an elliptical or a long linear incision is used followed by complete removal of the cyst and its sac.  The scar is usually big.



In the minimal incision-surgery, as the name implies, a minimal linear and small sub-centimeter-long incision is used.  Usually, the contents of the cyst are evacuated first to decrease the volume of the mass followed by complete removal of the capsule through the small incision.



Below are some illustrations.


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