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What Is a Trichilemmal Cyst?

Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon

A trichilemmal cyst, also known as a pilar cyst, is a growth that forms in a hair follicle, causing it to swell with fluid. These growths usually are benign, but a doctor might recommend removal if they cause pain or distress, because they are sometimes unpleasant to look at and are tender to the touch. Removal can take place in a clinic on an outpatient basis, and it does not take very long, especially if the dermatologist is skilled.

Trichilemmal cysts form thickened walls and swell over time beneath the surface of the skin. They can appear anywhere on the body and are especially common around the head and neck. A dermatologist can conduct a quick examination to determine the nature of the growth and might recommend removal. Sometimes the trichilemmal cyst is mistaken for a malignancy, in which case the doctor might request a biopsy to check on the cyst's contents.

Because they form in hair follicles, trichilemmal cysts are most common on the scalp.
Because they form in hair follicles, trichilemmal cysts are most common on the scalp.

To remove a trichilemmal cyst, the dermatologist typically administers a local anesthetic for the patient's comfort and excises the whole cyst. Some might drain the growth first and then pull out the shell of the cyst. The doctor might request a biopsy for safety if he or she has concerns about malignancy. Patients often need anti-inflammatory drugs after the procedure to address swelling and any residual inflammation left behind by the cyst.

A doctor may decide to perform a biopsy on a trichilemmal cyst.
A doctor may decide to perform a biopsy on a trichilemmal cyst.

In about 2 percent of cases, a trichilemmal cyst can turn malignant. These growths might include a proliferation of cells that can spread to neighboring tissues. For this reason, doctors often recommend removal even if a cyst doesn't appear to be a problem, to prevent the development of a cancerous growth. A patient who has a history of trichilemmal cysts should make sure to bring this up if he or she goes to the doctor to discuss a skin problem, because this could provide an important diagnostic clue.

A trichilemmal cyst should be examined by a dermatologist.
A trichilemmal cyst should be examined by a dermatologist.

Some families appear to have a genetic predisposition to trichilemmal cyst formation. Members of such families might want to stay alert to the early signs of cyst formation so they can get prompt treatment. It also can help to note the family history in patient charts to make doctors aware of the increased risk of cysts for a patient. This can be helpful when the doctor examines a patient who has a growth that appears ambiguous in nature; if the patient's family often develops trichilemmal cysts, the doctor might logically assume that this is the most likely explanation for the growth.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a WiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a WiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...

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    • Because they form in hair follicles, trichilemmal cysts are most common on the scalp.
      By: Paul Huxley
      Because they form in hair follicles, trichilemmal cysts are most common on the scalp.
    • A doctor may decide to perform a biopsy on a trichilemmal cyst.
      By: Radu Razvan
      A doctor may decide to perform a biopsy on a trichilemmal cyst.
    • A trichilemmal cyst should be examined by a dermatologist.
      By: michaeljung
      A trichilemmal cyst should be examined by a dermatologist.
    • A doctor may recommend a biopsy so the tissue can be examined under a microscope and cancer can be ruled out.
      By: luchschen_shutter
      A doctor may recommend a biopsy so the tissue can be examined under a microscope and cancer can be ruled out.
    • Trichilemmal cysts appear most commonly around the neck.
      By: Piotr Marcinski
      Trichilemmal cysts appear most commonly around the neck.
    • Some families have a genetic predisposition to trichilemmal cysts.
      By: Pavel Losevsky
      Some families have a genetic predisposition to trichilemmal cysts.
    • Doctors should be told about any family history of trichilemmal cysts.
      By: Gennadiy Poznyakov
      Doctors should be told about any family history of trichilemmal cysts.